Artificial leather, production method therefor, and artificial leather backing material

ABSTRACT

An artificial leather is provided having excellent flame retardancy and moderate air permeability and a flexible texture, where the artificial leather feels like natural suede and has an elegant appearance, the artificial leather including a fiber entanglement including an ultrafine fiber having an average single fiber diameter of 0.1 μm or more and 10 μm or less, and an elastomer, in which one surface is a napped surface having a raised nap, the other surface is a flame retardant surface having a flame retardant, and the following requirements 1 and 2 are satisfied: requirement 1: at least the flame retardant surface has a plurality of opening portions; requirement 2: the flame retardant has a tackiness of 0.1 N/cm2 or more and 2.0 N/cm2 or less.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. National Phase application ofPCT/JP2021/034748, filed Sep. 22, 2021 which claims priority to JapanesePatent Application No. 2020-163367, filed Sep. 29, 2020, the disclosuresof these applications being incorporated herein by reference in theirentireties for all purposes.

FIELD OF THE INVENTION

The present invention relates to an artificial leather which includes afiber entanglement including ultrafine fibers, an elastomer, and afunctional agent (flame retardant or the like), has moderate airpermeability and a flexible texture, is excellent in flame retardancy,and has feels like natural suede and an elegant appearance. The presentinvention also relates to an artificial leather backing material usedfor obtaining the artificial leather, and having good formability of anopening portion.

BACKGROUND OF THE INVENTION

Conventionally, an artificial leather including a fiber entanglementformed of ultrafine fibers and an elastomer and having raised nap hasexcellent characteristics in air permeability, durability, uniformity ofquality, and the like as compared with natural leather, and is used notonly as a clothing material but also in various fields such as interiormaterials of public transporters such as aircrafts, ships, and railroadvehicles, interior materials for vehicles, interior materials, buildingmaterials, and miscellaneous goods.

In the fields described above, artificial leather is often required tohave high flame retardant performance, and in the fields where flameretardancy is required, it is common that the artificial leatherincludes a flame retardant. Among them, in order to cope with aventilation system particularly in an interior material for vehicles,moderate air permeability is required by the density and materialconfiguration of artificial leather and control of an opening portion.

Meanwhile, in order to develop the flame retardancy in the artificialleather, methods such as applying a flame retardant to ultrafine fibers,applying the flame retardant to the entire artificial leather, andcoating and applying the flame retardant to one surface of theartificial leather are adopted.

However, in the artificial leather obtained by these methods, theelastomer such as polyurethane constituting the artificial leather andan ultrafine thermoplastic synthetic fiber constituting a nonwovenfabric, a woven fabric, or a knitted fabric are different from eachother in a mechanism developing flame retardancy, and therefore, it isknown that it is very difficult to make the entire artificial leatherflame retardant.

In order to solve such a problem of flame retardancy, it has beenproposed that an organic phosphorus component copolymerized polyester isused for ultrafine fibers of artificial leather (for example, see PatentDocument 1), a polyurethane elastomer obtained by copolymerizing anorganic phosphorus component is used for an elastomer of artificialleather (for example, see Patent Document 2), or a diarylphosphoramidate-based flame retardant is attached to ultrafine fibersand exhausted (for example, see Patent Document 3).

In addition, there have been proposed a method in which a base formed ofa flame-retardant heat-resistant fiber is stacked on a back surface andintegrated by entanglement (for example, see Patent Document 4), amethod in which a flame retardant is partially applied so as to have anarea ratio of 60 to 90% in order to secure a certain air permeabilitywhen the flame retardant is applied to a back surface of artificialleather (for example, see Patent Document 5), and a method in which ventholes penetrating the artificial leather are formed (for example, seePatent Document 6).

PATENT DOCUMENTS

-   Patent Document 1: Japanese Patent Laid-open Publication No.    2002-115183-   Patent Document 2: Japanese Patent Laid-open Publication No.    2002-201574-   Patent Document 3: Japanese Patent Laid-open Publication No.    2012-229508-   Patent Document 4: Japanese Patent Laid-open Publication No.    2014-25156-   Patent Document 5: Published Japanese Translation No. 2013-520581 of    the PCT International Publication-   Patent Document 6: International Publication 2014/097999

SUMMARY OF THE INVENTION

In the technique as disclosed in Patent Document 1, the organophosphoruscomponent is copolymerized as compared with polyester usually used forultrafine fibers, so that spinnability and dye dyeability at the time ofproduction are deteriorated. In addition, since thread strength ofultrafine fibers and rubbing fastness of the artificial leatherdecrease, it is difficult to use the artificial leather for applicationsrequiring high light resistance and high abrasion resistance.

In the technique as disclosed in Patent Document 2, the organophosphoruscomponent is copolymerized with a polyurethane component that is animportant constituent material for imparting strength and texture to theartificial leather without aged deterioration, and the design is suchthat texture and durability are lowered as compared with normalpolyurethane.

In the technique as disclosed in Patent Document 3, when the diarylphosphoramidate-based flame retardant is attached without using abinder, the flame retardant may fall off during use, and the flameretardancy becomes unstable. On the other hand, when the flame retardantis attached with a binder, a tactile sensation of a surface of theartificial leather becomes a hard feel. In addition, as disclosed in thebackground art of Patent Document 3, in a case where a water-solubleflame retardant such as guanidine phosphate is added to the entireartificial leather, when a napped surface is subjected to a process ofabsorbing moisture and then drying, there occurs a phenomenon that theguanidine phosphate is dissolved by the moisture and transferred to thesurface to form a cyclic stain, that is, so-called “water spot”, andthere is a problem that designability of the artificial leather issignificantly impaired.

In the technique as disclosed in Patent Document 4, it is necessary tohave a sufficient basis weight of the flame-retardant heat-resistantfiber in order to secure a certain flame retardancy, and denseness of anentangled structure of the artificial leather is reduced, so that anelegant appearance and a flexible texture tend to be impaired. A methodof integrating by entanglement by inserting into the inside andintertwining and integrating the flame-retardant heat-resistant fiberand a method of mixing flame-retardant heat-resistant fiber withconstituent fiber also have the same problem.

In the technique as disclosed in Patent Document 5, since the flameretardant is applied in a dot shape, sufficient flame retardancy is notobtained, and a preliminary artificial leather does not have sufficientair permeability, so that it is not possible to achieve both densenessfor an elegant appearance and air permeability that can be compatiblewith, for example, a ventilation system.

In the technique as disclosed in Patent Document 6, in the punching by apunching roll, a scrap after the punching is likely to clog a sheet orthe punching roll, and mass production is difficult.

To summarize the above, in the techniques as disclosed in PatentDocuments 1 to 6, in the artificial leather including a fiberentanglement formed of ultrafine fibers difficult to be made flameretardant and an elastomer, the artificial leather achieving both theflame retardancy and other important characteristics (in particular,moderate air permeability, flexible texture, feels like natural suede,and elegant appearance) cannot be provided.

Thus, the present invention has been made in view of the abovecircumstances, and an object thereof is to provide an artificial leatherhaving excellent functionality (flame retardancy and the like) whilehaving moderate air permeability and a flexible texture, and havingfeels like natural suede and an elegant appearance. Another object ofthe present invention is to provide an artificial leather backingmaterial used for obtaining the artificial leather, and having goodformability of an opening portion.

As a result of intensive studies by the present inventors to achieve theabove object, it has been found that in an artificial leather includingan ultrafine fiber entanglement, an elastomer, and a functional agent(flame retardant or the like), when the form of existence of thefunctional agent (flame retardant or the like) is within a specificrange and tackiness of the functional agent (flame retardant or thelike) is within a specific range, an artificial leather having goodformability and achieving both functionality (flame retardancy or thelike) and other important characteristics can be provided even if anopening portion is provided in the artificial leather.

The present invention has been completed based on these findings. Thepresent invention provides the following inventions.

The artificial leather of the present invention is an artificial leatherincluding a fiber entanglement including an ultrafine fiber having anaverage single fiber diameter of 0.1 μm or more and 10 μm or less, andan elastomer, in which one surface is a napped surface having a raisednap, the other surface is a flame retardant surface having a flameretardant, and the following requirements 1 and 2 are satisfied.

Requirement 1: At least the flame retardant surface has a plurality ofopening portions.

Requirement 2: The flame retardant has a tackiness of 0.1 N/cm² or moreand 2.0 N/cm² or less.

According to a preferred aspect of the artificial leather of the presentinvention, an opening ratio of the flame retardant surface is 1% or moreand 40% or less.

According to a preferred aspect of the artificial leather of the presentinvention, the artificial leather has a plurality of opening portions ineach of the napped surface and the flame retardant surface, and at leastsome of the opening portions are through opening portions formed topenetrate from the napped surface to the flame retardant surface.

According to a preferred aspect of the artificial leather of the presentinvention, the fiber entanglement is formed by integrating a fiberentanglement including the ultrafine fiber and a woven/knitted fabric(a).

According to a preferred aspect of the artificial leather of the presentinvention, the flame retardant surface is a surface formed by stacking awoven/knitted fabric (b).

According to a preferred aspect of the artificial leather of the presentinvention, a presence ratio of the flame retardant in a thicknessdirection satisfies the following formula:

0.001≤W/W ₀≤0.7

where W is a thickness (mm) from the flame retardant surface where theflame retardant is present, and W₀ is a thickness (mm) of the entireartificial leather.

According to a preferred aspect of the artificial leather of the presentinvention, the flame retardant contains a phosphorus-based compound.

According to a preferred aspect of the artificial leather of the presentinvention, the fiber entanglement including the elastomer has a densityof 0.20 g/cm³ or more and 0.50 g/cm³ or less.

In a production method for an artificial leather of the presentinvention, a flame retardant having a tackiness of 0.1 N/cm² or more and2.0 N/cm² or less is applied to one surface of a napped sheet-shapedarticle including a fiber entanglement including ultrafine fibers havingan average single fiber diameter of 0.1 μm or more and 10 μm or less andan elastomer to form a flame retardant surface, and a plurality ofopening portions are provided on at least the flame retardant surface.

An artificial leather backing material of the present invention is anartificial leather backing material including a fiber entanglementincluding an ultrafine fiber having an average single fiber diameter of0.1 μm or more and 10 μm or less, and an elastomer, in which one surfaceis a napped surface having a raised nap, the other surface is afunctional surface having a functional agent, and the functional agenthas a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less. Theartificial leather backing material can be used as the artificialleather of the present invention by forming an opening portion, and theartificial leather backing material itself can also be used as anartificial leather.

An artificial leather backing material of the present invention is anartificial leather backing material including a fiber entanglementincluding an ultrafine fiber having an average single fiber diameter of0.1 μm or more and 10 μm or less, and an elastomer, in which one surfaceis a napped surface having a raised nap, and the other surface is afunctional surface having a functional agent, the functional surface hasa Kinetic friction coefficient of 0.15 or more and 0.60 or less, and theartificial leather backing material has a stiffness of 30 mm or more and150 mm or less.

An artificial leather backing material of the present invention is anartificial leather backing material including a fiber entanglementincluding an ultrafine fiber having an average single fiber diameter of0.1 μm or more and 10 μm or less, and an elastomer, in which one surfaceis a napped surface having a raised nap, the other surface is afunctional surface having a functional agent, and an adhesion amount ofthe functional agent is 2 to 30% by mass with respect to the artificialleather backing material.

According to the present invention, it is possible to obtain anartificial leather having excellent functionality (flame retardancy andthe like) while having moderate air permeability and a flexible texture,and having feels like natural suede and an elegant appearance. Inaddition, it is possible to obtain an artificial leather backingmaterial used for obtaining the artificial leather, and having goodformability of an opening portion.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The artificial leather of the present invention is an artificial leatherincluding a fiber entanglement including an ultrafine fiber having anaverage single fiber diameter of 0.1 μm or more and 10 μm or less, andan elastomer, in which one surface is a napped surface having a raisednap, the other surface is a flame retardant surface having a flameretardant, and the following requirements 1 and 2 are satisfied.

Requirement 1: At least the flame retardant surface has a plurality ofopening portions.Requirement 2: The flame retardant has a tackiness of 0.1 N/cm² or moreand 2.0 N/cm² or less.

A ratio by weight of the ultrafine fiber contained in the fiberentanglement is preferably 60% or more, more preferably 80% or more.

An artificial leather backing material of the present invention is anartificial leather backing material including a fiber entanglementincluding an ultrafine fiber having an average single fiber diameter of0.1 μm or more and 10 μm or less, and an elastomer, in which one surfaceis a napped surface having a raised nap, the other surface is afunctional surface having a functional agent, and the functional agenthas a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less.

An artificial leather backing material of the present invention is anartificial leather backing material including a fiber entanglementincluding an ultrafine fiber having an average single fiber diameter of0.1 μm or more and 10 μm or less, and an elastomer, in which one surfaceis a napped surface having a raised nap, and the other surface is afunctional surface having a functional agent, the functional surface hasa Kinetic friction coefficient of 0.15 or more and 0.60 or less, and anartificial leather has a stiffness of 30 mm or more and 150 mm or less.

An artificial leather backing material of the present invention is anartificial leather backing material including a fiber entanglementincluding an ultrafine fiber having an average single fiber diameter of0.1 μm or more and 10 μm or less, and an elastomer, in which one surfaceis a napped surface having a raised nap, the other surface is afunctional surface having a functional agent, and an adhesion amount ofthe functional agent is 2 to 30% by mass with respect to the artificialleather backing material. Hereinafter, the constituent elements will bedescribed in detail, but the present invention is not limited to thescope described below at all as long as the gist thereof is notexceeded.

[Fiber Entanglement]

The fiber entanglement constituting the artificial leather of thepresent invention includes an ultrafine fiber, and the ultrafine fiberhas an average single fiber diameter of 0.1 μm or more and 10 μm orless. When the average single fiber diameter of the ultrafine fiber is0.1 μm or more, preferably 1.5 μm or more, an excellent effect ofcoloring property after dyeing, light resistance, fastness to rubbing,and stability during spinning is exhibited, and strength of theartificial leather that withstands practical use can be obtained. On theother hand, when the average single fiber diameter is 10.0 μm or less,preferably 6.0 μm or less, more preferably 4.5 μm or less, it ispossible to obtain an artificial leather that has flexibility, and denseand soft-to-the-touch surface quality.

In the present invention, the average single fiber diameter of ultrafinefiber is calculated by taking a scanning electron microscope (SEM)photograph of a cross-section of the artificial leather, randomlyselecting 10 ultrafine fibers having a circular shape or an ellipticalshape close to a circular shape, measuring the single fiber diameters,calculating the arithmetic average of the 10 fibers, and rounding thearithmetic average off to the first decimal place. However, whenultrafine fibers having an irregular cross-section are used, first, thecross-sectional area of the single fiber is measured, and the diameterof a hypothetical circle on the assumption that the cross-section wascircular is calculated to obtain the diameter of the single fiber.

As the ultrafine fiber of the fiber entanglement constituting theartificial leather of the present invention, various synthetic fibersincluding polyesters such as polyethylene terephthalate,polytrimethylene terephthalate, polytetramethylene terephthalate,polycyclohexylenedimethylene terephthalate,polyethylene-2,6-naphthalenedicarboxylate, andpolyethylene-1,2-bis(2-chlorophenoxy)ethane-4,4′-dicarboxylate,polyamides such as polyamide 6 and polyamide 66, polymers such asacrylic polyethylene and polypropylene, and the like can be used. Amongthese, polyester fibers formed of polymers such as polyethyleneterephthalate, polybutylene terephthalate and polytrimethyleneterephthalate, and the like are excellent in strength, dimensionalstability, light resistance and coloring properties and are thuspreferably used. Ultrafine fibers formed of different materials can bemixed in the fiber entanglement as long as the object of the presentinvention is not impaired.

The cross-sectional shape of the ultrafine fiber is circular from theviewpoint of processing operability, and it is also possible to employultrafine fibers having a modified cross-sectional shape such as anellipse, polygons such as a flattened polygon and a triangle, a fanshape, a cross shape, a hollow shape, a Y-shape, a T-shape, and aU-shape.

Inorganic particles such as titanium oxide particles, a lubricant, apigment, a thermal stabilizer, a UV absorber, a conductive agent, a heatstorage agent, an antibacterial agent, and the like can be added to theultrafine fibers forming the fiber entanglement according to variouspurposes.

In order to achieve excellent deep color developability in the presentinvention, a resin constituting the ultrafine fiber may be apolyester-based resin, and the polyester-based resin may contain apigment having an average particle diameter of 0.05 μm or more and 0.20μm or less. The particle diameter referred to herein is a particlediameter in a state in which the pigment is present in the ultrafinefiber, and generally refers to a particle diameter referred to as asecondary particle diameter. When the average particle diameter is 0.05μm or more, preferably 0.07 μm or more, the pigment is gripped insidethe ultrafine fiber, and therefore, falling off from the ultrafine fiberis suppressed. When the average particle diameter is 0.20 μm or less,preferably 0.18 μm or less, more preferably 0.16 μm or less, stabilityduring spinning and yarn strength are excellent. The average particlediameter is calculated by the following method.

-   -   (1) An ultrathin slice having a thickness of 5 to 10 μm is        prepared in a cross-sectional direction of a plane perpendicular        to a longitudinal direction of the ultrafine fiber.    -   (2) A fiber cross section in the ultrathin slice is observed        with a transmission electron microscope (TEM) at a magnification        of 10,000.    -   (3) Using image analysis software, an equivalent circle diameter        of the particle diameter of the pigment contained in a visual        field of 2.3 μm×2.3 μm of an observation image is measured at 20        points. When the number of pigment particles contained in the        visual field of 2.3 μm×2.3 μm is less than 20, the equivalent        circle diameter of the particle diameter of the existing pigment        is all measured.    -   (4) An average value (arithmetic average) is calculated for the        particle diameters at the measured 20 points.

In order to achieve excellent deep color developability in the presentinvention, when the resin constituting the ultrafine fiber is apolyester-based resin and a pigment is contained in the polyester-basedresin, the content of the pigment contained in the polyester-based resinforming the ultrafine fiber is preferably 0.5% by mass or more and 2.0%by mass or less with respect to the mass of the ultrafine fiber. Whenthe proportion of the pigment is 0.5% by mass or more, preferably 0.7%by mass or more, and more preferably 0.9% by mass or more, the deepcolor developability is excellent. When the proportion of the pigment is2.0% by mass or less, preferably 1.8% by mass or less, and morepreferably 1.6% by mass or less, an artificial leather having highphysical properties such as strength can be obtained. As the pigment,carbon-based black pigments such as carbon black and graphite, andoxide-based black pigments such as triiron tetraoxide and compositeoxides of copper and chromium can be used. The pigment is preferablycarbon black from the viewpoint of easily obtaining a pigment having asmall particle diameter and excellent dispersibility in a polymer. As achromatic fine-particle oxide pigment, a known pigment close to thetarget color can be used, and examples thereof include iron oxyhydroxide(e.g., “TM Yellow 8170” produced by Dainichiseika Color & Chemicals Mfg.Co., Ltd.), iron oxide (e.g., “TM Red 8270” produced by DainichiseikaColor & Chemicals Mfg. Co., Ltd.), and cobalt aluminate (e.g., “TM Blue3490E” produced by Dainichiseika Color & Chemicals Mfg. Co., Ltd.).

In the artificial leather of the present invention, a fiber entanglementincluding the ultrafine fiber is one of constituent elements. Examplesof the fiber entanglement include a woven fabric, a knitted fabric, anda nonwoven fabric, and the fiber entanglement further includes anelastomer inside or outside, and these may be properly used depending onthe cost and properties required for each application and purpose. Wovenand knitted fabrics are preferably used from the viewpoint of cost, andnonwoven fabrics, fiber entanglements filled with an elastomer, and thelike are preferably used from the viewpoint of texture with a sense offulfillment and quality due to fine naps.

In the case of using a woven/knitted fabric as the fiber entanglement,examples of the woven fabric include plain woven fabrics, twill wovenfabrics, satin woven fabrics, and various woven fabrics based on theseweave structures. As the knitted fabric, any of warp knitted fabrics,weft knitted fabrics represented by tricot knit fabrics, lace knitfabrics, and various knitted fabrics based on these knitting structuresmay be adopted.

In the case of using a nonwoven fabric as the fiber entanglement, allnonwoven fabrics described in various categories may be applied, such asgeneral short fiber nonwoven fabrics, long fiber nonwoven fabrics,needle punch nonwoven fabrics, papermaking nonwoven fabrics, spunbondnonwoven fabrics, meltblown nonwoven fabrics, and electrospun nonwovenfabrics. Here, a nonwoven fabric is preferable from the viewpoint of thetexture with a sense of fulfillment and the quality due to fine naps.

The inclusion of the elastomer inside or outside the fiber entanglementis more preferably used from the viewpoint of excellent durability andabrasion resistance of the artificial leather. In particular, it ispreferable that the elastomer is contained in the fiber entanglementfrom the viewpoint of flexibility.

In addition, in the artificial leather of the present invention, it ispreferable to integrate the fiber entanglement and a woven/knittedfabric (a) by entanglement from the viewpoint of excellent mechanicalstrength. More preferably, the fiber entanglement is a nonwoven fabric,and the woven/knitted fabric (a) is contained therein. Still morepreferably, a balance of appearance, flexibility, and strength isoptimized when the fiber entanglement is a nonwoven fabric and thewoven/knitted fabric (a) is a woven fabric.

In the woven/knitted fabric (a) integrated with the fiber entanglement,as the yarn that constitutes the woven/knitted fabric (a), syntheticfibers formed of polyester, polyamide, polyethylene, polypropylene,copolymers thereof, or the like are preferably used. Among these,synthetic fibers formed of polyester, polyamide and copolymers thereofmay be used singly or in combination or in mixture. As the yarn thatconstitutes the woven/knitted fabric (a), filament yarns, spun yarns,blended yarns of filaments and short fibers, and the like may be used.From the viewpoint of durability, particularly mechanical strength andthe like, it is more preferable to use a multifilament including apolyester-based resin or a polyamide-based resin.

When the average single fiber diameter of the fibers that constitute thewoven/knitted fabric (a) is 50.0 μm or less, more preferably 15.0 μm orless, and still more preferably 13.0 μm or less, not only an artificialleather excellent in flexibility is obtained, but also even when thefibers of the woven/knitted fabric are exposed on the surface of theartificial leather, a hue difference from the ultrafine fiber containingthe pigment after dyeing is reduced, so that uniformity of a hue of thesurface is not impaired. On the other hand, when the average singlefiber diameter of the fibers that constitute the woven/knitted fabric(a) is 1.0 μm or more, more preferably 8.0 μm or more, and still morepreferably 9.0 μm or more, shape stability of a product as an artificialleather is improved. The average single fiber diameter of the fibersthat constitute the woven/knitted fabric (a) is calculated by taking ascanning electron microscope (SEM) photograph of the cross-section ofthe artificial leather, randomly selecting 10 fibers constituting thewoven fabric, measuring the single fiber diameter of the fiber,calculating the arithmetic average of the 10 fibers, and rounding thearithmetic average off to the first decimal place. When the fibers thatconstitute the woven/knitted fabric (a) are multifilaments, a totalfineness of the multifilaments is measured according to “8.3.1 Finenessbased on corrected mass b) Method B (simple method)” in “8.3 Fineness”in JIS L 1013: 2010 “Chemical fiber filament yarn test method”, and ispreferably 30 dtex or more and 170 dtex or less. When the total finenessof the yarns that constitute the woven/knitted fabric (a) is 170 dtex orless, an artificial leather excellent in flexibility is obtained. On theother hand, when the total fineness is 30 dtex or more, not only theshape stability of a product as the artificial leather is improved, butalso when the fiber entanglement is a nonwoven fabric, the fibers thatconstitute the woven/knitted fabric (a) are less likely to be exposed onthe surface of the artificial leather when the woven/knitted fabric (a)is integrated by entanglement by needle punching or the like, which ispreferable. When the woven/knitted fabric (a) is a woven fabric, themultifilaments of the warp and the weft preferably have the same totalfineness. In addition, the yarns constituting the woven fabricpreferably have a twist count of 1000 T/m or more and 4000 T/m or less.When the twist count is 4000 T/m or less, more preferably 3500 T/m orless, and still more preferably 3000 T/m or less, an artificial leatherexcellent in flexibility is obtained. When the twist count is 1000 T/mor more, more preferably 1500 T/m or more, and still more preferably2000 T/m or more, in a case where a nonwoven fabric and a woven fabricare integrated by entanglement by needle punching or the like, damage tofibers constituting the woven fabric can be prevented, and themechanical strength of the artificial leather is excellent, which ispreferable.

As the woven/knitted fabric (a), a woven/knitted fabric containing acomposite fiber (hereinafter, described as a side-by-side compositefiber in some cases) in which two or more kinds of polymers are combinedin a side-by-side or eccentric sheath-core type may also be used. Forexample, in a side-by-side composite fiber formed of two or more kindsof polymers having different intrinsic viscosities (IV), differentinternal strains are generated between the two components by stressconcentration on the high viscosity side during stretching. Because ofthis internal strain, the high viscosity side shrinks greatly by thedifference in elastic recovery after stretching and the difference inthermal shrinkage in the heat treatment process, and strain is generatedin the single fiber to develop a three-dimensional coil type crimp. Bythis three-dimensional coil type crimp, stretchability as artificialleather is developed.

When the fiber entanglement is a nonwoven fabric, a nonwoven fabric canprovide an appearance and a texture that are uniform and elegant whenthe surface of the nonwoven fabric is napped. Examples of the form ofthe nonwoven fabric include a long fiber nonwoven fabric mainly composedof filaments and a short fiber nonwoven fabric mainly composed of fibersof 100 mm or less. When the long fiber nonwoven fabric is used as afibrous substrate, an artificial leather having excellent strength canbe obtained, which is preferable. On the other hand, in the case of theshort fiber nonwoven fabric, the number of fibers oriented in thethickness direction of the artificial leather can be increased ascompared with the case of the long fiber nonwoven fabric, and thesurface of the artificial leather when napped can have a high densefeeling.

The fiber length of the ultrafine fibers in the case where a short fibernonwoven fabric is used is preferably 25 mm or more and 90 mm or less.When the fiber length is 90 mm or less, more preferably 80 mm or less,and still more preferably 70 mm or less, good quality and texture areobtained. On the other hand, when the fiber length is 25 mm or more,more preferably 35 mm or more, and still more preferably 40 mm or more,an artificial leather with excellent abrasion resistance can beobtained.

The basis weight of the fiber entanglement including the ultrafine fiberthat constitutes the artificial leather according to the presentinvention is measured according to “6.2 Mass per Unit Area (ISO method)”in “Test methods for nonwovens” of JIS L 1913: 2010, and is preferablyin a range of 50 g/m² or more and 600 g/m² or less. When the basisweight of the nonwoven fabric is 50 g/m² or more, more preferably 100g/m² or more, an artificial leather having a sense of fulfillment and anexcellent texture can be obtained. On the other hand, when the basisweight is 600 g/m² or less, more preferably 450 g/m² or less, a softartificial leather having excellent moldability can be obtained. Evenwhen the woven/knitted fabric (a) is integrated by entanglement, thebasis weight of the fiber entanglement is preferably in theabove-described basis weight range.

[Elastomer]

Next, the artificial leather of the present invention has an elastomer.Preferably, the elastomer is contained in the fiber entanglement. Byincluding the elastomer inside, the softness, shape stability, andabrasion resistance of the artificial leather are improved. Unlike afunctional agent (flame retardant or the like) to be described later,the elastomer is required to have a purpose as a binder of the fiberentanglement.

As the elastomer, polyurethane, styrene-butadiene rubber (SBR), nitrilerubber (NBR), acrylic resin, and the like may be used, and it is apreferred aspect to use polyurethane as the main component among these.Use of polyurethane can afford an artificial leather having touch havingfeels like natural suede, an elegant appearance, and physical propertiesenough to endure actual use.

The polyurethane forming the elastomer preferably contains a blackpigment (b) having an average particle diameter of 0.05 μm or more and0.20 μm or less and a coefficient of variation (CV) of 75% or less.

The particle diameter referred to herein is a particle diameter in astate in which the black pigment (b) is present in the elastomer, andgenerally refers to a particle diameter referred to as a secondaryparticle diameter.

When the average particle diameter is 0.05 μm or more, preferably 0.07μm or more, the black pigment (b) is gripped inside the elastomer, andtherefore, falling off from the ultrafine fiber is suppressed. When theaverage particle diameter is 0.20 μm or less, preferably 0.18 μm orless, more preferably 0.16 μm or less, dispersibility is excellent whenthe elastomer is impregnated.

When the coefficient of variation (CV) of the particle diameter is 75%or less, preferably 65% or less, more preferably 60% or less, still morepreferably 55% or less, and most preferably 50% or less, a distributionof the particle diameter becomes small, and falling off of smallparticles from a surface of the elastomer, precipitation ofsignificantly aggregated particles in an impregnation tank, and the likeare suppressed.

In the present invention, the average particle diameter and thecoefficient of variation (CV) are calculated by the following method.

-   -   (1) An ultrathin slice having a thickness of 5 to 10 μm is        prepared in a cross-sectional direction of a plane perpendicular        to a longitudinal direction of the artificial leather.    -   (2) A cross section of the elastomer in the ultrathin slice is        observed with a transmission electron microscope (TEM) at a        magnification of 10,000.    -   (3) Using image analysis software, an equivalent circle diameter        of the particle diameter of the black pigment (b) contained in a        visual field of 2.3 μm×2.3 μm of an observation image is        measured at 20 points. When the number of particles of the black        pigment (b) contained in the visual field of 2.3 μm×2.3 μm is        less than 20, the equivalent circle diameter of the particle        diameter of the existing black pigment (b) is all measured.    -   (4) The average value (arithmetic average) and the coefficient        of variation (CV) are calculated for the particle diameters at        the measured 20 points. In the present invention, the        coefficient of variation is calculated by the following        equation:

Coefficient of variation of particle diameter (%)=(standard deviation ofparticle diameter)/(arithmetic average of particle diameter)×100.

As the black pigment (b) in the present invention, carbon-based blackpigments such as carbon black and graphite, and oxide-based blackpigments such as triiron tetraoxide and composite oxides of copper andchromium can be used. The black pigment is preferably carbon black fromthe viewpoint of easily obtaining a pigment having a small particlediameter and excellent dispersibility in a polymer.

As the polyurethane used in the present invention, either organicsolvent-based polyurethane used in the state of being dissolved in anorganic solvent or water-dispersible polyurethane used in the state ofbeing dispersed in water can be used. Polyurethane obtained by reactionof a polymer diol, an organic diisocyanate, and a chain extender ispreferably used as polyurethane to be used for the present invention.

For example, a polycarbonate-based diol, polyester-based diol,polyether-based diol, silicone-based diol, or fluorine-based diol can beused as the aforementioned polymer diol, and a copolymer of acombination of these diols can also be used. Among them, it is apreferred aspect to use a polycarbonate-based diol from the viewpoint ofhydrolysis resistance and abrasion resistance.

A polycarbonate-based diol as described above can be produced, forexample, through ester exchange reaction between alkylene glycol andester carbonate or through reaction of phosgene or a chloroformate withalkylene glycol.

Examples of the alkylene glycol include linear alkylene glycols such asethylene glycol, propylene glycol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, 1,9-nonanediol, and 1,10-decanediol, branched alkyleneglycols such as neopentyl glycol, 3-methyl-1,5-pentanediol,2,4-diethyl-1,5-pentanediol, and 2-methyl-1,8-octanediol, alicyclicdiols such as 1,4-cyclohexanediol, aromatic diols such as bisphenol A,and glycerin, trimethylolpropane, and pentaerythritol. In the presentinvention, either a polycarbonate-based diol obtained from a singlealkylene glycol or a copolymerized polycarbonate-based diol obtainedfrom two or more alkylene glycols can be adopted.

Examples of the polyester-based diols include polyester diols producedby condensing one of various low molecular weight polyols and apolybasic acid.

For example, one or a plurality selected from the following can be usedas the low molecular weight polyol described above: ethylene glycol,1,2-propylene glycol, 1,3-propylene glycol, 1,3-butane diol, 1,4-butanediol, 2,2-dimethyl-1,3-propane diol, 1,6-hexane diol,3-methyl-1,5-pentane diol, 1,8-octane diol, diethylene glycol,triethylene glycol, dipropylene glycol, tripropylene glycol,cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol.

Adducts prepared by adding various alkylene oxides to bisphenol A arealso usable.

Furthermore, for example, one or a plurality selected from the followingcan be used as the polybasic acid: succinic acid, maleic acid, adipicacid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacicacid, dodecane dicarboxylic acid, phthalic acid, isophthalic acid,terephthalic acid, and hexahydroisophthalic acid.

Examples of the polyether-based diols used in the present inventioninclude polyethylene glycol, polypropylene glycol, polytetramethyleneglycol, and copolymerized diols which are formed by combining thesesubstances.

The number average molecular weight of the polymer diol is preferably ina range of 500 or more and 4000 or less when the molecular weight of apolyurethane-based elastomer is constant. When the number averagemolecular weight is preferably 500 or more, more preferably 1,500 ormore, it is possible to prevent the artificial leather from becominghard. When the number average molecular weight is 4000 or less, or morepreferably 3000 or less, the polyurethane can maintain its strength.

Examples of the organic diisocyanate used in the present inventioninclude aliphatic diisocyanates such as hexamethylene diisocyanate,dicyclohexylmethane diisocyanate, isophorone diisocyanate, and xylylenediisocyanate, and aromatic diisocyanates such as diphenylmethanediisocyanate and tolylene diisocyanate. These compounds can also be usedin combination.

As the chain extender, amine chain extenders such as ethylenediamine andmethylenebisaniline, and diol chain extenders such as ethylene glycolcan be preferably used. Furthermore, a polyamine which is obtained byreacting polyisocyanate and water can also be used as a chain extender.

The polyurethane used in the present invention may be used incombination with a crosslinker with the aim of improving waterproofness,abrasion resistance, hydrolysis resistance, and the like. Thecrosslinker may be an external crosslinker that is added as a thirdcomponent to polyurethane, or an internal crosslinker that introducesreaction points to form a crosslinked structure in advance into thepolyurethane molecular structure. It is preferable to use an internalcrosslinker from the viewpoint that crosslinking points can be formedmore uniformly in the polyurethane molecular structure and that thedecrease in flexibility can be mitigated.

The crosslinking agent used may be a compound having an isocyanategroup, an oxazoline group, a carbodiimide group, an epoxy group, amelamine resin, a silanol group and the like.

The elastomer may contain various additives including flame retardantssuch as “phosphorus, halogen, and inorganic flame retardants”;antioxidants such as “phenolic, sulfur, and phosphorus antioxidants”;ultraviolet absorbers such as “benzotriazole, benzophenone, salicylate,cyanoacrylate, and oxalic acid anilide UV absorbers”; light stabilizerssuch as “hindered amine and benzoate light stabilizers”; hydrolysisstabilizers such as polycarbodiimide; plasticizers; antistatic agents;surfactants; coagulation modifiers; and dyes according to purposes.

In general, the content of the elastomer in the artificial leather canbe appropriately adjusted in consideration of the type of the elastomerto be used, a production method for the elastomer, and the texture andphysical properties; however, in the present invention, the content ofthe elastomer is preferably 10% by mass or more and 60% by mass or lesswith respect to the mass of the fiber entanglement. When the content ofthe elastomer is preferably 10% by mass or more, more preferably 15% bymass or more, still more preferably 20% by mass or more, the bondingbetween the fibers by the elastomer can be enhanced, and the abrasionresistance of the artificial leather can be improved. On the other hand,when the content of the elastomer is preferably 60% by mass or less,more preferably 45% by mass or less, still more preferably 40% by massor less, the flexibility of the artificial leather can be furtherincreased.

According to a preferred aspect of the artificial leather of the presentinvention, the density of the fiber entanglement including theelastomer, that is, the density of the fiber entanglement with theelastomer (the density of the woven/knitted fabric (b) described laterand the artificial leather containing no flame retardant) is preferably0.20 g/cm³ or more and 0.50 g/cm³ or less. When the density is 0.20g/cm³ or more, preferably 0.25 cm³, the shape stability, dimensionalstability, and strength of the artificial leather become sufficient. Inaddition, the artificial leather becomes dense, and the opening portionbecomes a clean opening portion without fraying or the like. On theother hand, when the density is 0.50 g/cm³ or less, preferably 0.45g/cm³ or less, the air permeability and flexibility of the artificialleather are improved.

[Functional Agent (Flame Retardant or the Like)]

The functional agent used in the present invention refers to an agentthat imparts functionality such as flame retardancy, antifoulingproperties, yellowing resistance, NOx resistance, grip properties, waterrepellency, oil repellency, color migration resistance, abrasionresistance, odor resistance, durability, flexibility, and stretchabilityto a fibrous product. The functional agent (flame retardant or the like)used for the artificial leather of the present invention has tackinessof 0.1 N/cm² or more and 2.0 N/cm² or less. When the tackiness of thefunctional agent (flame retardant or the like) is 0.10 N/cm² or more,preferably 0.15 N/cm² or more, and more preferably 0.20 N/cm² or more,the functional agent (flame retardant or the like) is secured to thefiber entanglement with sufficient adhesiveness during application anddrying of the functional agent (flame retardant or the like), and thefunctional agent (flame retardant or the like) after drying does notfall off even in a high-temperature environment. When the tackiness is2.00 N/cm² or less, preferably 1.60 N/cm² or less, and more preferably1.00 N/cm² or less, after the formation of the opening, the fiber dustscomposed of the fiber, the elastomer, and the functional agent (flameretardant or the like) are not clogged in the opening, and theformability of the opening portion is improved, and when the formationof the opening portion is punching, continuous processing can beperformed without clogging the needle hole. In addition, a structure inwhich the functional agent (flame retardant or the like) is uniformlydispersed and bonded is obtained, and the texture of the artificialleather becomes flexible. In the present invention, the tackiness of thefunctional agent (flame retardant or the like) is a value obtained bymeasurement and calculation as follows.

-   -   (1) A functional agent (flame retardant or the like) is heated        to 60° C.    -   (2) Using a tack meter, a stainless steel probe (contact        pressure 24.5 N/cm²) is pressed against the functional agent        (flame retardant or the like) at a speed of 6 mm/min, and held        for 5 seconds.    -   (3) After (2), a maximum load at the time of peeling at 6 mm/min        is read.    -   (4) (2) to (3) are repeated five times, and the arithmetic        average of the resulting values is rounded off to the second        decimal place.

In order to stably obtain the adhesiveness, opening properties, andsoftness even when there is a temperature change, the tackiness when thefunctional agent (flame retardant or the like) is heated to 40° C. ispreferably 0.05 N/cm² or more and 1.00 N/cm² or less, and the tackinessat 20° C. is preferably 0.01 N/cm² or more and 0.50 N/cm² or less. Inparticular, the tackiness at 20° C. is preferable when the stickiness ofthe surface of the functional surface (surface of the flame retardant orthe like) is small as handleability such as molding or sewing of anartificial leather sheet at room temperature. When the tackiness of thefunctional agent is within the above range, resistance is reduced whenthe artificial leather is unwound from the roll shape, and thehandleability of the artificial leather is improved in the work of thenext step. When the functional agent (flame retardant or the like) isheated to 40° C. or 20° C., the tackiness is measured in the same manneras described above except that the heating temperature in (1) is changedto 40° C. or 20° C.

Although the functional agent (flame retardant or the like) may be aresin itself composed of a polymer compound having an active functionalgroup, in addition to a low molecular compound having a functionalcomponent (flame retardant component or the like), it is preferable tocontain a resin in order to obtain durability of functionality, and theresin is selected from, for example, an acrylic resin, a urethane resin,a polyester resin, a vinyl acetate resin, and the like, is notparticularly limited, and is preferably an acrylic resin having a goodbalance from the viewpoint of adhesiveness to a fiber entanglement and awoven/knitted fabric, heat resistance, and adhesiveness. An amount ofthe binder resin to be blended is not limited to a specific value, andis preferably in a range of 5 to 50% by mass with respect to a totalmass of the functional component (flame retardant component or the like)contained in the functional agent (flame retardant or the like). Whenthe blending amount is 5% by mass or less, the flame retardant is likelyto cause falling off of a powder component, and when the blending amountexceeds 50% by mass, the texture of the artificial leather may beimpaired. From the viewpoint of the tackiness, for example, a resinhaving low rubber elasticity is preferably used. For example, regardingthe acrylic resin, an acrylamide-based acrylic resin is more preferablethan an acrylonitrile-based acrylic resin because the tackiness isbetter. In general, many resins have a hard texture, and the texture canbe softened by reducing the blending amount of the resin. When anethylene-vinyl acetate resin having high adhesiveness is used, theadhesiveness and the tackiness are enhanced even in a small amount;therefore, when it is desired to reduce the blending amount of theresin, it is preferable to contain ethylene-vinyl acetate.

When the functional agent is a flame retardant and a combustion mode isa carbonization type, as the resin of the flame retardant, other resinssuch as acrylic resins, SBR resins, and MBR resins may also be used,provided they do not affect the carbide formation of vinyl acetate,vinyl acetate copolymer resins, or the like. In particular, if the flameretardant is made to further include an acrylic resin, the advantages ofsoftened texture and improved water resistance of the flame retardantare obtained.

The type of the flame retardant component of the flame retardant is notparticularly limited, and the flame retardant component is preferablywater-insoluble or sparingly water-soluble from the viewpoint of waterspot. The “water spot” as used herein refers to a phenomenon in which,in the artificial leather to which a flame retardant is added, whenmoisture typified by water droplets adheres from either side of thefront and back surfaces and the artificial leather is then naturallydried, the wet portion becomes a white spot or stain. From the viewpointof adapting to recent environmental hormone regulations, it ispreferable to use a dehalogenated flame retardant. Examples of thedehalogenated flame retardant include phosphorus-containing compounds,nitrogen-containing compounds, phosphorus-nitrogen compounds,sulfoamide-based compounds, phosphorus-sulfoamide-based compounds, andsulfur-containing nitrogen-based compounds, and these can be used aloneor in combination of two or more thereof. From the viewpoint of theflame retardant performance, a phosphorus-based compound is preferable,and examples of the phosphorus-based compound include guanidine-basedcompounds, carbamate-based compounds, phosphate ester-based compounds,phosphate ester-amide-based compounds, ammonium polyphosphate compounds,and aromatic phosphate ester-based compounds such as triphenyl phosphateand trixylenyl phosphate. Particularly, an ammonium polyphosphate flameretardant having a high phosphorus content is preferable, and a typecovered with a melamine resin or a silicon oxide resin is preferable forfurther making the flame retardant sparingly water-soluble. As theinorganic flame retardant, known flame retardants such as aluminumhydroxide, titanium oxide, zinc oxide, expandable graphite, magnesiumhydroxide, calcium carbonate, zinc borate, ammonium polyphosphate, andred phosphorus can be used, and it is preferable to use apolyphosphate-based flame retardant excellent in processability anddurability.

As the combustion mode of the flame retardant, there are a carbonizationtype for forming a carbonized film and a melting type for dropping afire source, and although any mode is not limited, the melting type ispreferable from the viewpoint of flame retardant stability in flameretardant evaluation in the case of sufficient flame retardancy.

In the artificial leather of the present invention, in the evaluation ofthe flame retardancy, based on burning test standard (horizontal burningrate) of automobile interior material of Federal Motor Vehicle SafetyStandards (FMVSS) No. 302, a test piece (350 mm×100 mm) is heldhorizontally, a 38 mm flame is allowed to remain for 15 seconds, and theflame retardancy is evaluated by a burning rate with respect to 254 mmbetween a gauge line A and a gauge line B according to the followingcriteria.

In the case where the flame self-extinguishes before reaching the gaugeline A, a judgment classification is “non-combustible”, and the productis judged as acceptable.

In the case where the flame self-extinguishes after the gauge line A,and the burning distance is within 50 mm and the burning time was within60 seconds, the judgment classification is “self-extinguished”, and theproduct is judged as acceptable.

In the case where the flame does not self-extinguish but the burningrate between the gauge lines is 4 inches/min (about 101.6 mm/min) orless, the judgment classification is “burning at rate not more thanspecified rate”, and the product is judged as acceptable.

In the case where the flame does not self-extinguish and the burningrate between the gauge lines exceeds 4 inches/min (about 101.6 mm/min),the judgment classification is “burning at rate exceeding specifiedrate”, and the composite sheet product is judged as unacceptable.

For example, when a carbonization type agent such as an antifoulingagent is applied to the artificial leather, since the flame retardant isof the carbonization type, the carbonization amount increases, the flameretardancy improves, and the combustion mode can be selected accordingto the material configuration of the artificial leather. When thecarbonization type is selected for the flame retardant, by selecting aresin that is easily carbonized for the resin of the flame retardant,the above-described flame retardant component can be reduced, which ispreferable from the viewpoint of cost. For example, there is a vinylgroup-containing resin that forms a carbonized skeleton duringcombustion.

It is preferable that the vinyl group-containing resin contains at leastone selected from a vinyl acetate resin, an ethylene-vinyl acetatecopolymer resin, an acrylic vinyl acetate copolymer resin, a vinylacetate vinyl copolymer resin, and a branched fatty acid vinyl acetatecopolymer resin, since the formation of a carbide by using the vinylacetate resin or the vinyl acetate copolymer resin in combination with aphosphorus-based compound promotes flame retardancy, and particularlyexhibits an effect of improving flame retardant properties forhorizontal burning of the artificial leather.

An adhesion amount of the flame retardant is required to be determinedfrom the viewpoint of securing necessary flame retardant performance andreducing texture curing, and increases or decreases depending on thebasis weight, thickness, and ultrafine fiber of the artificial leather,the polymer type of the elastomer, and the fiber entanglement type;however, it is preferable to contain the flame retardant in an amount of2 to 30% by mass with respect to the artificial leather from theviewpoint of achieving both the flame retardancy and the texture. Anapplication amount of the flame retardant is preferably 10 to 200 g/m²,and more preferably within a range of 20 to 100 g/m². Although theadhesion amount of the flame retardant can be calculated by, forexample, mass after application−mass after application, when theadhesion amount is calculated from the artificial leather afterapplication, the adhesion amount can also be calculated using elementalpeak analysis such as fluorescent X-rays.

As a solution used for applying the flame retardant to the artificialleather, it is preferable that the viscosity is 500 to 10000 mPa·s atnormal temperature from the viewpoint of coating permeability, and aviscosity modifier may be contained as necessary. The viscosity is morepreferably 1500 to 9000 mPa·s, and still more preferably 2500 to 7000mPa·s. In this way, a presence ratio of the flame retardant describedlater in the thickness direction falls within a suitable range, and anartificial leather that is more flexible and has high flame retardancycan be obtained. The method for measuring the viscosity of the solutionis not particularly limited, but a measurement method using a commonlyused rotational viscometer is used. The viscosity modifier used foradjusting the viscosity of the solution is preferably poorly soluble inwater from the viewpoint of preventing occurrence of water spot, and ispreferably, for example, an alkali-thickened acrylic resin or anethylene oxide higher fatty acid ether.

In the present invention, in addition to the components described above,aluminum hydroxide, magnesium hydroxide, a metal oxide, and the like canalso be used as a flame retardant aid for the flame retardant.

The adhesion amount of the functional agent (flame retardant or thelike) is required to be determined from the viewpoint of securingnecessary functional performance and reducing texture curing, and theopening properties of the artificial leather backing material, andincreases or decreases depending on the basis weight, thickness, andultrafine fiber of the artificial leather, the polymer type of theelastomer, and the fiber entanglement type; however, it is preferable tocontain the functional agent in an amount of 2 to 30% by mass withrespect to the artificial leather from the viewpoint of satisfying theabove characteristics. An application amount of the functional agent(flame retardant or the like) is preferably 10 to 200 g/m², and morepreferably within a range of 20 to 100 g/m².

[Woven/Knitted Fabric (b)]

In the artificial leather of the present invention, the functionalsurface (surface of flame retardant or the like) is preferably a surfaceformed by stacking the woven/knitted fabric (b). That is, by adopting anaspect in which the woven/knitted fabric (b) is further stacked to thefiber entanglement on the functional surface (surface of flame retardantor the like) side opposite to the napped surface of the artificialleather, the artificial leather has more strength and also hasflexibility. In this case, the fiber entanglement may include thewoven/knitted fabric (a) as described above, and a suitablewoven/knitted fabric can be selected according to the purpose of each ofthe woven/knitted fabric (a) and the woven/knitted fabric (b).

As for the kind of the woven/knitted fabric (b) used in the presentinvention, it is possible to use any of various kinds of knitted fabricssuch as warp knitted fabrics and weft knitted fabrics typified by tricotknitted fabrics, lace knitted fabrics, and knitted fabrics based onthese knitting methods, and various kinds of woven fabrics such as plainweave fabrics, twill weave fabrics, satin weave fabrics, and wovenfabrics based on these weaving methods. In a preferred aspect, a knittedfabric having high air permeability and high stretchability is used asthe woven/knitted fabric (b).

As for the kind of the yarn that constitutes the woven/knitted fabric(b), for example, a filament yarn, a spun yarn, or a blended yarn of afilament yarn and short fibers can be used.

The density of the woven/knitted fabric (b) is preferably 0.10 g/cm³ ormore and 0.60 g/cm³ or less. When the density of the woven/knittedfabric (b) is 0.10 g/cm³ or more, more preferably 0.15 g/cm³ or more, anartificial leather having good shape retention can be obtained. On theother hand, when the density of the woven/knitted fabric (b) is 0.60g/cm³ or less, more preferably 0.50 g/cm³ or less, the functional agent(flame retardant or the like) can be penetrated to the inside, and anartificial leather excellent in flexibility can be obtained.

The thickness of the woven/knitted fabric (b) is preferably 0.10 to 2.50mm, more preferably 0.15 to 1.50 mm, and still more preferably 0.20 to1.00 mm. If the thickness of the woven/knitted fabric (b) is less than0.10 mm, the processability and strength at the time of sticking withthe fiber entanglement are deteriorated, and if the thickness exceeds2.50 mm, the flexibility of the air permeability tends to be impaired.

The method of stacking the fiber entanglement and the woven/knittedfabric (b) is not limited, and a method of bonding the fiberentanglement and the woven/knitted fabric (b) with an adhesiveinterposed therebetween is common. Examples of the adhesive includethermoplastic resins such as a polyester resin, a copolymerizedpolyester resin, a nylon resin, and an acrylic resin, andmoisture-curable resins such as a silicone rubber, a polystyrene rubber,and a polyurethane resin. A thermoplastic resin excellent in workabilityis preferably used and, in particular, a nylon resin excellent inhydrolysis resistance is preferably used. In the artificial leatherincluding the ultrafine fiber, a moisture-curable resin capable of beingprocessed with a low thermal history is preferable from the viewpoint ofimproving rubbing fastness.

A thickness of an adhesive layer is preferably 1 to 300 μm as long asthe adhesive layer has sufficient bondability and does not impair theflexibility and air permeability of the artificial leather.

In the case where a thermoplastic resin is used as the adhesive, thesoftening temperature of the thermoplastic resin is preferably 70 to160° C., more preferably 80 to 120° C. If the softening temperature islower than 70° C., the thermoplastic resin may be softened during theprocessing or actual use. If the softening temperature is higher than160° C., the texture of the artificial leather and the rubbing fastnessmay be impaired by the softening treatment at the time of sticking.

[Artificial Leather]

The artificial leather of the present invention includes the fiberentanglement and the elastomer, and one surface is a napped surfacehaving a raised nap, and the other surface is a flame retardant surfacehaving the flame retardant.

First, in the artificial leather of the present invention, one surfaceis the napped surface having the raised nap. That is, the raised nap maybe provided only on the surface to be a product surface of theartificial leather, and is also allowed to be provided on both surfaces.As for the form of raised nap in the case where the artificial leatherhas raised nap on the surface to be the product surface, the raised nappreferably has a length and direction flexibility to such an extent thattraces remain when the artificial leather is stroked with a finger, thatis, a so-called finger mark remain due to the change of direction of theraised nap from the viewpoint of design effects. Examples of the formhaving raised nap on the other surface (back surface) with respect tothe product surface of the artificial leather include imparting a flameretardant after forming raised nap on the back surface of the fiberentanglement. When the woven/knitted fabric (b) is stacked on the backsurface of the fiber entanglement, the front and back surfaces of thefiber entanglement are napped, and the flame retardant is added to thesurface of the stacked woven/knitted fabric (b), so that the flameretardant is present in the napped portion of the back surface of thefiber entanglement, and the flame retardant surface has raised nap.

More specifically, when the surface to be the product surface is thenapped surface, the raised napped length on the surface is preferably 50μm or more and 500 μm or less, and more preferably 100 μm or more and450 μm or less. When the raised nap length is 50 μm or more, the raisednap covers the elastomer, and the exposure of the elastomer on theproduct surface of the artificial leather is suppressed, so that anelegant appearance can be obtained. When the woven/knitted fabric (a) isentangled and integrated with the fiber entanglement constituting theartificial leather, or when the fiber entanglement itself includes awoven/knitted fabric, setting the raised nap length within the aboverange can sufficiently cover a tissue of the woven/knitted fabric in thevicinity of the product surface of the artificial leather, which ispreferable in that a naturally-like and elegant appearance can beobtained. On the other hand, when the raised nap length is 500 μm orless, an artificial leather excellent in design effect and abrasionresistance can be obtained.

In the present invention, the raised nap length of the artificialleather is calculated by the following method.

-   -   (1) A thin slice with a thickness of 1 mm in the cross-sectional        direction of a plane perpendicular to the longitudinal direction        of the artificial leather is prepared in the state of the raised        nap of the artificial leather being ruffled by using a lint        brush, etc.    -   (2) A cross-section of the artificial leather is observed at        90-fold magnification by means of a scanning electron microscope        (SEM).    -   (3) In an SEM image photographed, the height of a raised nap        portion (layer including only ultrafine fiber) is measured at 10        points at intervals of 200 μm in the width direction of the        cross-section of the artificial leather.    -   (4) With respect to the measured height of the raised nap        portion (layer including only ultrafine fiber) at 10 points, the        average value (arithmetic average) is calculated.

In the artificial leather of the present invention, it is important tohave a plurality of opening portions in the functional surface (surfaceof flame retardant or the like). The “opening portion” in the presentinvention is not limited to a portion where a hole (through openingportion) formed by penetrating an artificial leather from the nappedsurface to the functional surface (surface of flame retardant or thelike) is opened, and includes, for example, a case where the openingportion does not overlap the woven/knitted fabric (b) in a planardirection and is not the through opening portion. Examples of the latterinclude a form in which an opening portion is formed in advance in thewoven/knitted fabric (b) containing the functional agent (flameretardant or the like) and the woven/knitted fabric (b) is stacked onthe fiber entanglement. The shape of the opening portion can be anyshape according to a desired design, and polygonal shapes such as around shape, an elliptical shape, a flat shape, and a triangular shape,a fan shape, a cross shape, and deformed shapes such as a hollow shape,a Y shape, a T shape, and a U shape can be adopted. An arrangementpattern of the opening portion is not particularly limited, and theopening portion may be regularly provided or irregularly provided;however, from the viewpoint of exhibiting uniform air permeability andstrength throughout the artificial leather, the opening portions arepreferably regularly arranged at predetermined intervals. A holediameter of the opening portion is preferably 0.1 to 3.0 mm and morepreferably 0.5 to 2.5 mm from the viewpoint of achieving both airpermeability and strength of the entire artificial leather.

In addition, in the artificial leather of the present invention, anopening ratio of the functional surface (surface of flame retardant orthe like) is preferably 1% or more and 40% or less from the viewpoint ofachieving both air permeability and strength of the entire artificialleather. That is, when the opening ratio is 1% or more, more preferably2% or more, an artificial leather excellent in air permeability can beobtained. On the other hand, when the opening ratio is 40% or less, morepreferably 20% or less, and still more preferably 15% or less, anartificial leather excellent in strength can be obtained.

The artificial leather of the present invention has a plurality ofopening portions in each of the napped surface and the functionalsurface (surface of flame retardant or the like), and at least some ofthe opening portions are the through opening portions formed topenetrate from the napped surface to the functional surface (surface offlame retardant or the like). With this configuration, an artificialleather having more excellent air permeability can be obtained.

The shape of the through opening portion in the thickness direction maybe, for example, a cylindrical through opening portion in which the holediameters of the opening portion of the napped surface and the openingportion of the functional surface (surface of flame retardant or thelike) are the same, or a mortar-shaped through opening portion in whichthe hole diameters of the opening portion of the napped surface and theopening portion of the functional surface (surface of flame retardant orthe like) are different. That is, the shape of the through openingportion can be selected in consideration of the design and mechanicalproperties of the artificial leather.

In the artificial leather of the present invention, the presence ratioof the functional agent (flame retardant or the like) in the thicknessdirection preferably satisfies the following formula:

0.001≤W/W ₀≤0.7

where W is the thickness (mm) from the functional surface (surface offlame retardant or the like) where the functional agent (flame retardantor the like) is present, and W₀ is the thickness (mm) of the entireartificial leather. When the presence ratio of the functional agent(flame retardant or the like) in the thickness direction is 0.001 ormore, more preferably 0.01 or more, still more preferably 0.05 or more,an artificial leather excellent in functionality (flame retardancy orthe like) can be obtained. On the other hand, when the presence ratio ofthe functional agent (flame retardant or the like) in the thicknessdirection is 0.7 or less, more preferably 0.5 or less, and still morepreferably 0.3 or less, an artificial leather excellent in airpermeability and flexibility can be obtained.

The presence ratio of the functional agent (flame retardant or the like)in the thickness direction is obtained by collecting and preparing threeSEM measurement samples, randomly selecting five points in anobservation image of each cross section, measuring W and W₀ at eachpoint, and calculating W/W₀ using an arithmetic average value. When thefunctional agent (flame retardant or the like) cannot be specified froma normal SEM image, for example, calculation is performed using a methodof determining a resin containing an element peak as the functionalagent by SEM-EDX. For example, in the case of the flame retardant,calculation is performed using a method of determining a resincontaining a phosphorus element peak as the flame retardant.

As a preferred form of the artificial leather, a form in which thewoven/knitted fabric (b) is stacked on the fiber entanglement and thefunctional agent (flame retardant or the like) is unevenly distributedin the woven/knitted fabric (b) is preferable from the viewpoint offunctionality (flame retardancy or the like).

As a preferable form of the functional surface (surface of flameretardant or the like) of the artificial leather, it is preferable thatthe functional agent (flame retardant or the like) is present on thesurface of the functional surface (surface of flame retardant or thelike), and an area ratio of the functional agent (flame retardant or thelike) of the functional surface (surface of flame retardant or the like)is 10 to 100%. The area ratio is obtained by collecting and preparingthree SEM measurement samples, randomly selecting five points in anobservation image of 50 times of the surface of each functional surface(surface of flame retardant or the like), photographing a SEM image,binarizing the SEM image, and then performing calculation by using avalue obtained by arithmetically averaging the area ratio in which thefunctional agent (flame retardant or the like) is present with respectto a total area obtained by excluding the opening portion from an imagearea of 50 times. When the area ratio is preferably 10% or more, morepreferably 30% or more, an artificial leather excellent in functionality(flame retardancy or the like) and functional (flame retardant, etc.)stability can be obtained, and for example, when a polyurethane foam islaminated on the back surface of an artificial leather such as aninterior material for vehicles, smoothness of the functional surface(surface of flame retardant or the like) increases, so that e peelstrength with the polyurethane foam increases.

The artificial leather of the present invention preferably has athickness of 0.2 mm or more and 2.5 mm or less as measured according to“6.1.1 A method” in “6.1 Thickness (ISO method)” in “Test methods fornonwovens” of JIS L 1913: 2010 When the thickness of the artificialleather is 0.2 mm or more, more preferably 0.3 mm or more, and stillmore preferably 0.4 mm or more, not only excellent processability at thetime of production is obtained, but also a sense of fulfillment andexcellent texture are obtained. On the other hand, when the thickness is2.5 mm or less, more preferably 2.0 mm or less, and still morepreferably 1.5 mm or less, a soft artificial leather having excellentmoldability can be obtained.

In the artificial leather of the present invention, the rubbing fastnessmeasured by a “9.1 friction tester type I (clock meter) method”according to JIS L 0849: 2013 “Test methods for color fastness torubbing” and light fastness measured by a “7.2 Exposure method a) Firstexposure method” according to JIS L 0843: 2006 “Test method for colorfastness to light of xenon arc lamp” are each preferably grade 3 orhigher. When the rubbing fastness and the light fastness are grade 3 orhigher, it is possible to prevent color loss and contamination ofclothes and the like during actual use.

In the artificial leather of the present invention, the mass loss of theartificial leather after 20,000 times of abrasion under a pressing loadof 12.0 kPa in an abrasion test measured in accordance with “8.19.5Method E (Martindale method)” of “8.19 Abrasion strength and colorchange by rubbing” of JIS L 1096:2010 “Cloth experiment method of wovenfabric and knitted fabric” is preferably 20 mg or less, more preferably15 mg or less, still more preferably 10 mg or less. When the mass lossis 20 mg or less, fluff dropping during actual usage can be prevented.

In the artificial leather of the present invention, the tensile strengthas measured in accordance with “6.3.1 Tensile strength and percentageelongation (ISO method)” in “Test methods for nonwovens” of JIS L 1913:2010 is preferably from 20 to 400 N/cm in arbitrary measurementdirection. When the tensile strength is 20 N/cm or more, more preferably30 N/cm or more, and still more preferably 40 N/cm or more, theartificial leather is excellent in shape stability and durability, whichis preferable. When the tensile strength is 400 N/cm or less, morepreferably 300 N/cm or less, and still more preferably 250 N/cm or less,an artificial leather excellent in moldability is obtained.

The artificial leather of the present invention preferably has astiffness of 30 to 150 mm as measured by a cantilever method in “8.21Stiffness” of JIS L 1096:2010 “Cloth experiment method of woven fabricand knitted fabric”, from the viewpoint of texture and flexibility, andmore preferably 50 to 130 mm.

In the artificial leather of the present invention, the air permeabilityis preferably 1 to 400 cm³/cm²/sec, more preferably 20 to 300cm³/cm²/sec, and still more preferably 70 to 250 cm³/cm²/sec in order toachieve both flame retardancy and air permeability in Method A (Fraziertype method) of “8.26 Air permeability” of JIS L 1096: 2010 “Clothexperiment method of woven fabric and knitted fabric”. In the presentinvention, the air permeability is greatly affected by the opening;however, when the fiber entanglement has air permeability, the fiberentanglement is better from the viewpoint of sweatiness andmultiplication of bacteria. Therefore, the air permeability of the fiberentanglement having no opening portion is preferably 1 to 100cm³/cm²/sec, more preferably 2 to 50 cm³/cm²/sec.

The basis weight of the artificial leather of the present invention ismeasured according to “6.2 Mass per Unit Area (ISO method)” in “Testmethods for nonwovens” of JIS L 1913: 2010, and is preferably in a rangeof 50 g/m² or more and 800 g/m² or less. When the basis weight of thenonwoven fabric is 50 g/m² or more, more preferably 100 g/m² or more,still more preferably 150 g/m² or more, an artificial leather having asense of fulfillment and an excellent texture can be obtained. On theother hand, when the basis weight is 800 g/m² or less, more preferably600 g/m² or less, and still more preferably 500 g/m² or less, a softartificial leather having excellent moldability can be obtained.

From the viewpoint of the texture and flexibility of the artificialleather after formation of the opening, the artificial leather backingmaterial for producing the artificial leather having the opening portionaccording to the present invention preferably has a stiffness of 30 mmor more and 150 mm or less, more preferably 50 mm or more and 130 mm orless, as measured by the cantilever method in “8.21 Stiffness” of JIS L1096: 2010 “Cloth experiment method of woven fabric and knitted fabric”.When the stiffness is 30 mm or more and 150 mm or less, an openingportion is easily formed in the artificial leather backing material, andfor example, when the opening portion is formed with a hollow punch suchas a hole piercing punch, waste of the artificial leather backingmaterial hollowed out at the opening portion tends to come out from thehollow portion of the punch, so that productivity of opening formingprocessing is improved.

In the artificial leather backing material of the present invention, theKinetic friction coefficient of the functional surface is preferably0.15 or more and 0.60 or less in terms of the formability of the openingportion and the productivity of opening forming processing. A frictioncoefficient affects slipperiness of the functional agent and an openingdevice (punch, hollow needle, drill, etc.), for example, in the case ofan opening method is perforation (punch, hollow needle, etc.) anddrilling.

In the artificial leather backing material of the present invention, theadhesion amount of the functional agent is preferably 2 to 30% by masswith respect to the artificial leather backing material in terms of theproperties of the artificial leather described above, the formability ofthe opening, and the productivity of opening forming processing. Whenthe adhesion amount of the functional agent is less than 2% by mass,fiber waste hollowed out at the opening portion of the artificialleather backing material is likely to be loosened, and for example, inthe case of a punch, it is difficult to remove the fiber waste from thehollow portion. When the adhesion amount of the functional agent is morethan 30% by mass, for example, in the case of the punch, the hollowportion is likely to be clogged with the waste. The adhesion amount canbe calculated from a weight change before and after applicationsimilarly to the adhesion amount, and can also be calculated by chemicalanalysis such as fluorescent X-ray.

[Production Method for Artificial Leather]

The artificial leather of the present invention is preferably producedby applying a flame retardant having a tackiness of 0.1 N/cm² or moreand 2.0 N/cm² or less to one surface of a napped sheet-shaped articleincluding a fiber entanglement including ultrafine fibers having anaverage single fiber diameter of 0.1 μm or more and 10 μm or less and anelastomer to form a flame retardant surface, and providing a pluralityof opening portions on at least the flame retardant surface to have.Hereinafter, the details of each step will be described.

<Step of Producing Ultrafine Fiber-Generating Fibers>

The ultrafine fiber constituting the artificial leather of the presentinvention can be produced by a conventionally known method, and examplesof the method include a sea-island spinning method, a mixed spinningmethod, and a split type composite spinning method in synthetic fiberproduction. It is preferable to use ultrafine fiber-generating fibersincluding two or more kinds of polymer substances having differentsolubilities in a solvent in terms of productivity such as formation ofthe fiber entanglement.

In an ultrafine fiber generation step, an island portion formed of aresin to be an ultrafine fiber is formed, and an ultrafinefiber-generating fiber having a sea-island type composite structure inwhich an easily soluble polymer forms a sea portion is produced.

As the ultrafine fiber-generating fiber, an islands-in-the-sea fiber isused in which thermoplastic resins having different solvent solubilitiesare used as a sea portion (easily soluble polymer) and an island portion(hardly soluble polymer), and the sea portion is dissolved and removedusing a solvent or the like to cause the island portion to form anultrafine fiber. Use of the islands-in-the-sea fiber is favorable inview of the texture or surface quality of the artificial leather,because at the time of removing the sea portion, a suitable gap can beprovided between island portions, that is, between ultrafine fibersinside a fiber bundle.

As the method of spinning the ultrafine fiber-generating fiber having asea-island composite structure, a method using a mutually arrangedpolymer body in which a spinneret for sea-island composite fibers isused and the fiber is spun by mutually arranging a sea portion and anisland portion is preferred from the viewpoint that ultrafine fibershaving a uniform single fiber fineness are obtained.

As a method of incorporating the pigment into the island portion, evenwhen spinning is performed using a resin chip obtained by kneading thepigment with the resin of the island portion, any method can be adoptedin which a master batch obtained by kneading the pigment with the resinis prepared in advance, and the master batch and chips of another resinare mixed and spun.

As the sea portion of the islands-in-the-sea fibers, for example, acopolymerized polyester obtained by copolymerizing polyethylene,polypropylene, polystyrene, sodium sulfoisophthalic acid, polyethyleneglycol or the like, and polylactic acid can be used, but polystyrene orcopolymerized polyester is preferably used from the viewpoint of yarnmaking property, easy elutability, and the like.

In the production method for an artificial leather of the presentinvention, in the case of using the islands-in-the-sea fiber, anislands-in-the-sea fiber in which the strength of the island portion is2.5 cN/dtex or more is preferably used. When the strength of the islandportion is 2.5 cN/dtex or more, more preferably 2.8 cN/dtex or more,still more preferably 3.0 cN/dtex or more, the abrasion resistance ofthe artificial leather is enhanced, and at the same time, reduction inthe rubbing fastness due to falling off of the fiber can be suppressed.

In the present invention, the strength of the island portion of theislands-in-the-sea fibers is calculated by the following method.

-   -   (1) 10 islands-in-the-sea fibers having a length of 20 cm are        bundled.    -   (2) The sea portion is dissolved and removed from the sample of        (1), and an air drying is performed.    -   (3) A test is performed 10 times (N=10) in accordance with        “8.5.1 Standard time test” of “8.5 Tensile strength and        percentage elongation” of JIS L 1013:2010 “Testing methods for        man-made filament yarns” under the conditions of a grasp        interval of 5 cm, a tensile speed of 5 cm/min, and a load of 2        N.    -   (4) A value obtained by rounding the arithmetic average value        (cN/dtex) of the test results of (3) to the first decimal place        is employed as the strength of the island portion of the        islands-in-the-sea fiber.

<Step of Producing Fiber Entanglement>

A conventional production method for a fiber entanglement in whichultrafine fibers or islands-in-the-sea fibers are used as awoven/knitted fabric and a nonwoven fabric can be applied. Preferably,the spun-out ultrafine fiber-generating fiber is opened and passedthrough a cross wrapper, etc. to form a fiber web, and the fiber web isthen entangled to obtain a nonwoven fabric. As the method for obtainingthe nonwoven fabric by entangling the fiber web, a needle punchingtreatment, a water jet punching treatment, and the like can be used.

As for the form of the nonwoven fabric, either a short-fiber nonwovenfabric or a long-fiber nonwoven fabric may be used as described above,and in the case of the short-fiber nonwoven fabric, the number of fibersoriented in the thickness direction of the artificial leather is largerthan that in the long-fiber nonwoven fabric, and the surface of theartificial leather at the time of being napped can give a highly densefeeling.

In the case where a short-fiber nonwoven fabric is used for the nonwovenfabric, the obtained ultrafine fiber-generating fibers are preferablycrimped, cut to a predetermined length to obtain a raw cotton, thenopened, stacked, and entangled, thereby obtaining a short-fiber nonwovenfabric. Generally known methods may be used for the crimping and cuttingsteps.

In addition, when the artificial leather includes the woven/knittedfabric (a), the obtained nonwoven fabric and the woven/knitted fabric(a) are stacked and then integrated by entanglement. For theentanglement and integration of the nonwoven fabric and thewoven/knitted fabric (a), the woven/knitted fabric (a) is stacked on onesurface or both surfaces of the nonwoven fabric, or the woven/knittedfabric (a) is sandwiched between a plurality of nonwoven fabric webs,and then the fibers of the nonwoven fabric and the woven/knitted fabric(a) can be interlaced by needle punching, water jet punching, or thelike.

The apparent density of the nonwoven fabric including ultrafinefiber-generating fibers after needle punching or water jet punching ispreferably 0.15 g/cm³ or more and 0.45 g/cm³ or less. Preferably, whenthe apparent density is 0.15 g/cm³ or higher, the sheet-shaped articleshould have sufficient shape stability and dimension stability. Inaddition, preferably, when the apparent density is 0.45 g/cm³ or lower,a sufficient space can be kept such that the elastomer is imparted.

It is also preferable for the nonwoven fabric to be subjected to heatshrinkage treatment with warm water or steam to improve the densefeeling of the fibers.

Then, the nonwoven fabric may be impregnated with an aqueous solution ofa water-soluble resin and dried to add the water-soluble resin to thenonwoven fabric. Adding the water-soluble resin to the nonwoven fabricfixes the fibers and improves the dimensional stability.

<Step of Generating Ultrafine Fiber>

When the islands-in-the-sea fiber is used, in this step, the obtainedfibrous substrate is treated with a solvent to generate ultrafine fibershaving an average single fiber diameter of single fibers of 0.1 μm ormore and 10 μm or less.

The development of ultrafine fibers is carried out by immersing thenonwoven fabric formed of islands-in-the-sea fibers in a solvent toensure dissolution and removal of the sea portion of theislands-in-the-sea fibers.

When the ultrafine fiber-generating fiber is an islands-in-the-sea fiberand the sea portion is polyethylene, polypropylene or polystyrene, anorganic solvent such as toluene or trichloroethylene can be used as thesolvent to dissolve and remove the sea portion. An aqueous alkalisolution of sodium hydroxide or the like can be used when the seaportion is copolymerized polyester or polylactic acid. Hot water can beused when the sea portion is water-soluble thermoplastic polyvinylalcohol-based resin.

<Step of Adding Elastomer>

In this step, a fiber entanglement including ultrafine fibers orultrafine fiber-generating fibers as a main component is impregnatedwith a solution of an elastomer and solidified to add the elastomer. Themethod of fixing the elastomer to the fiber entanglement may be a methodof impregnating a solution of the elastomer into the fiber entanglementand then subjecting the resultant to wet coagulation or dry coagulation,and these methods can be appropriately selected according to the kind ofthe used elastomer.

N,N′-dimethylformamide, dimethyl sulfoxide, or the like is preferablyused as the solvent used when polyurethane is added as the elastomer. Awater-dispersible polyurethane liquid in which polyurethane is dispersedas an emulsion in water may be used.

The elastomer may be applied to the fiber entanglement before generatingultrafine fibers from the ultrafine fiber-generating fibers, or aftergenerating ultrafine fibers from the ultrafine fiber-generating fibers.

<Step of Half-Cutting and Grinding Fiber Entanglement IncludingElastomer>

From the viewpoint of production efficiency, it is also a preferableaspect that after the completion of the step above, the fiberentanglement provided with the elastomer is cut in half in the thicknessdirection to form half-cut sheets as two fiber entanglements.

Furthermore, a napped surface can be formed by applying a nappingtreatment to the fiber entanglement provided with the elastomer or ahalf-cut sheet-shaped article obtained by cutting in half. The nappingtreatment can be performed by grinding the surface using sandpaper or aroll sander. The napping treatment can be applied to only one surface orboth surfaces.

When the napping treatment is applied, a lubricant such as a siliconeemulsion can be added to the surface of the fiber entanglement beforethe napping treatment. In addition, when an antistatic agent is appliedbefore the napping treatment, a ground powder generated by grinding isless likely to deposit on sandpaper. In this way, a napped sheet-shapedarticle having a napped surface is formed.

<Step of Dyeing Napped Sheet-Shaped Article>

It is preferable for the napped sheet-shaped article to be dyed.Examples of the dyeing treatment include jet dyeing treatment using ajigger dyeing machine or a jet dyeing machine, dip dyeing treatment suchas thermosol dyeing treatment using a continuous dyeing machine, andprinting treatment to the napped surface, such as roller printing,screen printing, inkjet printing, sublimation printing, and vacuumsublimation printing. In particular, a jet dyeing machine is preferablyused from the viewpoint of quality and appearance from the viewpoint ofobtaining a flexible texture. If necessary, the artificial leather maybe subjected to various kinds of resin finishing after the dyeing.

<Step of Stacking and Integrating Woven/Knitted Fabric (b)>

It is preferable that the woven/knitted fabric (b) is stacked andintegrated with an adhesive on a surface opposite to a napped surface(when both surfaces each have a napped surface, the napped surface on aside to be a product surface) of the napped sheet. Examples of themethod of adding the adhesive include a method of applying apredetermined amount of the adhesive using a device such as a rotaryscreen, a knife roll coater, a gravure roll coater, a kiss roll coater,or a calender coater. In particular, it is preferable to form adiscontinuous adhesive layer using a rotary screen or a gravure rollcoater because the artificial leather has a good texture. Forming adiscontinuous adhesive layer can prevent texture curing and reduction inair permeability of the artificial leather. The discontinuous adhesivelayer means an adhesive layer including both a portion where an adhesiveis present and a portion where an adhesive is absent with respect to anadhesion surface, that is, a horizontal surface of the woven/knittedfabric or raised nap sheet. For example, the discontinuous adhesivelayer means an adhesive layer in which the adhesive is arranged in a dotpattern.

As a bonding method, when a thermoplastic resin is used as an adhesive,the adhesive can be integrated by thermocompression bonding. For thethermocompression bonding, a method such as heat rolls can be used. Inthe case where heat rolls are used, it is preferable to set thetemperature of the heat roll on the woven/knitted fabric side higherthan the temperature of the heat roll on the skin sheet side. When awet-curable resin is used as an adhesive, adhesion is promoted under asuitable temperature and humidity environment called curing.

The roll temperature on the woven/knitted fabric side inthermocompression bonding with heat rolls is preferably 80 to 180° C.,more preferably 100 to 160° C. If the roll temperature on thewoven/knitted fabric side is lower than 80° C., adhesion takes time, anda large load is imposed on the process. If the roll temperature on thewoven/knitted fabric side is higher than 180° C., the texture of theartificial leather becomes coarse and hard.

<Step of Adding Functional Agent (Flame Retardant or the Like)>

A functional agent (flame retardant or the like) is added to one surfaceof the napped sheet-shaped article to form a functional surface (surfaceof flame retardant or the like), thereby obtaining an artificial leatherbacking material. Here, the functional agent (flame retardant or thelike) having a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less isapplied to obtain the functional surface (surface of flame retardant orthe like). Alternatively, the functional surface has a Kinetic frictioncoefficient (JIS K 7125) of 0.15 or more and 0.60 or less, and theartificial leather backing material has a stiffness of 30 mm or more and150 mm or less. In this step, the functional surface (surface of flameretardant or the like) is formed on a surface opposite to the nappedsurface (when both surfaces each have a napped surface, the nappedsurface on the side to be a product surface) of the napped sheet-shapedarticle.

Examples of the method of forming the functional surface (surface offlame retardant or the like) include a method of applying the functionalagent (flame retardant or the like) to a stacked sheet obtained bystacking the napped sheet-shaped article or the woven/knitted fabric (b)by using a device such as a rotary screen, a knife roll coater, agravure roll coater, a kiss roll coater, or a calender coater. Althoughthe functional agent (flame retardant or the like) may be applied by apadding treatment and migrated by drying to be unevenly distributed to asurface layer, stability of unevenly distributed to the surface layer ispoor. The napping treatment may be further performed after thefunctional agent (flame retardant or the like) is applied and dried.Alternatively, the functional agent (flame retardant or the like) may beapplied to the woven/knitted fabric (b) in advance, and then thewoven/knitted fabric (b) may be stacked on the surface opposite to thenapped surface (when both surfaces each have the napped surface, thenapped surface on the side to be a product surface) of the nappedsheet-shaped article to form a functional surface (surface of flameretardant or the like).

Since the functional agent (flame retardant or the like) permeates theinside after being applied, the functional agent (flame retardant or thelike) is permeated while adjusting the viscosity of the functional agent(flame retardant or the like), a mesh of a gravure roll, the applicationamount, an immersion amount, and the like. As a drying method after theapplication of the functional agent (flame retardant or the like), thedrying can be performed using a known dryer such as a tenter dryer.

<Step of Forming Opening>

Then, the functional (flame retardant or the like) sheet including thefunctional surface (surface of flame retardant or the like) has aplurality of opening portions at least on the functional surface(surface of flame retardant or the like). Examples of the means forproviding the opening portion include methods such as boring such asperforation and drilling, and laser processing. The opening portion maybe formed not only on the functional surface (surface of flame retardantor the like) but also on the other surface. The timing of opening is notlimited, and for example, the fiber entanglement and the woven/knittedfabric (b) may be separately opened and then stacked and integrated.Preferably, the functional agent (flame retardant or the like) isapplied to the stacked sheet, and a through opening portion is formed bya drill, a perforated needle, or a hole piercing punch. The artificialleather is obtained by forming the opening portion.

Since the artificial leather after the opening portion is formed has asmaller contact area than before the opening, the Kinetic frictioncoefficient of the functional surface decreases. For example, from theviewpoint of stacking a polyurethane foam on the functional surface byframe lamination or the like, or from the viewpoint of handleability inthe next step, the Kinetic friction coefficient of the functionalsurface is preferably 0.10 to 0.55 as the artificial leather having theopening portion.

<Post-Processing Step>

In addition, in the artificial leather, it is also possible to providean artificial leather in which a design may be applied to its surface asnecessary. For example, the surface may be subjected to post processingsuch as embossing, laser processing, pinsonic processing, and printingprocessing.

The artificial leather of the present invention obtained by theproduction method exemplified above is excellent in functionality (flameretardancy and the like) while having moderate air permeability and aflexible texture, has feels like natural suede and an elegantappearance, and can be widely used for an interior material forvehicles, interior materials, building materials, and miscellaneousgoods, and in particular, the artificial leather is suitably used forthe interior material for vehicles because of its excellentfunctionality (flame retardancy and the like). In addition, theartificial leather backing material of the present invention obtained bythe production method exemplified above is excellent in openingformability, and is suitably used for the production of the artificialleather.

EXAMPLES

Next, the artificial leather of the present invention will be describedmore specifically using Examples, but the present invention is notlimited only to these Examples. Unless otherwise described, physicalproperties are measured based on the methods described above.

[Measuring Methods and Processing Methods for Evaluation]

(1) Average Single-Fiber Diameter of Ultrafine Fiber (μm)

In the measurement of the average single fiber diameter of ultrafinefibers, the average single fiber diameter was calculated by observingthe ultrafine fibers by means of a scanning electron microscope, Model“VW-9000”, manufactured by Keyence Corp.

(2) Abrasion Resistance of Artificial Leather

After 20,000 times of abrasion under a pressing load of 12.0 kPa in anabrasion test measured in accordance with “8.19.5 Method E (Martindalemethod)” of “8.19 Abrasion strength and color change by rubbing” of JISL 1096:2010 “Cloth experiment method of woven fabric and knittedfabric”, an abrasion state of the artificial leather surface wasobserved and compared with the surface state before the test, and adegree of abnormality was judged according to the following grade. Inthis evaluation, grades 3 to 5 were regarded as acceptable.

-   -   Grade 5: not recognized at all.    -   Grade 4: slightly recognized; however, hardly conspicuous.    -   Grade 3: apparently recognized; however, less conspicuous.    -   Grade 2: somewhat remarkable abnormality is recognized.    -   Grade 1: considerably remarkable abnormality is recognized.

(3) Tensile strength of artificial leather Two specimen sheets of 2cm×20 cm were sampled in an arbitrary direction of the artificialleather, and the tensile strength specified in accordance with “6.3.1Tensile strength and percentage elongation (ISO method)” in “Testmethods for nonwovens” of JIS L 1913: 2010 was measured. In themeasurement, the average of two sheets was employed as the tensilestrength of the artificial leather.

(4) Appearance Quality and Feel of Artificial Leather

The appearance quality and feel of the artificial leather were evaluatedby a total of 20 evaluators consisting of 10 healthy adult men and 10healthy adult women and after visually deciding the following ratings,the most common rating was employed as the appearance quality and feelof the artificial leather. In the case of a tie between ratings, ahigher rating was employed as the quality and feel of the artificialleather. The acceptance level of the present invention was “A, B, or C”.

-   -   A: Elegant appearance like natural leather, dense surface touch,        and premium luxurious feeling    -   B: Although inferior to natural leather, slightly elegant        appearance, slightly dense surface touch, and moderate luxurious        feeling    -   C: Artificial elegance and surface touch, and low luxurious        feeling    -   D: Less elegant, rough surface touch, and felt as low-cost        product

(5) Evaluation of Air Permeability of Artificial Leather

For each artificial leather to be measured, a 200 mm×200 mm test piecewas taken from five different positions and subjected to measurementaccording to Method A (Frazier type method) of “8.26 Air permeability”of JIS L 1096: 2010 “Cloth experiment method of woven fabric and knittedfabric”, followed by calculating the quantity of air (cm³/cm²/sec)passing through the test piece based on the conversion table attached tothe test apparatus. In addition, the five calculations thus obtainedwere averaged to give a value to be adopted as the air permeability(cm³/cm²/sec).

(6) Test of Flexibility of Artificial Leather

Based on the cantilever method described in “8.21 Stiffness” of JIS L1096: 2010 “Cloth experiment method of woven fabric and knitted fabric”,the flexibility of the artificial leather was evaluated by preparing atest piece of 2 cm×15 cm, placing the test piece on a horizontal tablehaving a 45° slope, making the test piece to glide, and reading thescale when a middle point at one end of the test piece was in contactwith the slope.

(7) Flame Retardant Performance Test of Artificial Leather

As described above, evaluation was performed based on the burning teststandard (horizontal burning rate) of the automobile interior materialof Federal Motor Vehicle Safety Standards (FMVSS) No. 302. The size ofthe test piece at this time was 350 mm×100 mm.

(8) Test of Water Spot Properties of Artificial Leather

An artificial leather sample was placed, 3 cm³ of water was addeddropwise onto the surface, the sample was allowed to stand until it wasnaturally dried, and then the occurrence of ring stain and the like onthe sample surface was observed. A case where the ring stain and thelike were visually clearly conspicuous was determined to beunacceptable.

(9) Opening Ratio of Artificial Leather

The opening ratio refers to an area ratio of the opening portion in theentire area on one surface of the artificial leather, and refers to anarea ratio on the surface. A 20 cm×20 cm sample of the artificialleather was scanned by image photographing, an operation of calculatingthe area ratio by binarization processing was performed on the sample at5 points, and the area ratio was determined by arithmetic average.

(10) Presence Ratio of Flame Retardant in Thickness Direction

The presence ratio of the flame retardant in the thickness direction wascalculated by the above method after observing the cross section of theartificial leather by using the scanning electron microscope (SEM),Model “VW-9000”, manufactured by Keyence Corp.

(11) Density of Fiber Entanglement Including Elastomer

The density of the fiber entanglement including the elastomer (thedensity of the woven/knitted fabric (b) and the artificial leathercontaining no flame retardant) shown in Examples and ComparativeExamples was calculated by measuring the basis weight of the fiberentanglement to which the elastomer was added (including thewoven/knitted fabric (a) when there was the woven/knitted fabric (a))according to “6.2 Mass per Unit Area (ISO method)” in “Test methods fornonwovens” of JIS L 1913: 2010 as described above, and dividing thebasis weight by the thickness of the fiber entanglement to which theelastomer was added. Five samples were randomly taken out from the fiberentanglement sample including the elastomer, and the average value wastaken as the density.

Density (g/cm³)=basis weight (g/m²)÷thickness (mm)÷1000).

(12) Tackiness of Functional Agent

Measurement and calculation were performed according to the followingprocedure.

-   -   (1) The functional agent was heated to 60° C.    -   (2) Using a tack meter (Tack Taster TA-500 manufactured by        Universal Building Materials Co., Ltd.), a stainless steel probe        (contact pressure 24.5 N/cm²) was pressed against the functional        agent (flame retardant or the like) at a speed of 6 mm/min, and        held for 5 seconds.    -   (3) After (2), a maximum load at the time of peeling at 6 mm/min        was read.    -   (4) (2) to (3) were repeated five times, and the arithmetic        average of the resulting values was rounded off to the second        decimal place to obtain the tackiness at 60° C.

(13) Kinetic Friction Coefficient

Three test pieces of 80 mm×200 mm were taken from the artificialleather, and the functional surface was measured at a test speed of 100mm/min, with a sliding piece of 63 mm×63 mm, and at a load of 1.92 Naccording to JIS K 7125, and the average value was taken as the Kineticfriction coefficient.

Example 1

<Step of Producing Raw Stock>

While polyethylene terephthalate was used as the island component,polystyrene was used as the sea component, and the island component andthe sea component were subjected to melt spinning using a sea-islandcomposite spinneret having 16 islands under the conditions of anisland/sea mass ratio of 80/20, a discharge rate of 1.2 g/(min·hole),and a spinning speed of 1,100 m/min, and then 2.7-fold stretching wasperformed in a spinning oil solution bath set at 90° C. Then, crimpingwas performed using a stuffer box crimper, followed by cutting to alength of 51 mm to provide raw stock of islands-in-the-sea fiber with asingle fiber fineness of 3.8 dtex.

<Step of Producing Fiber Entanglement>

The raw stock obtained as described above was used to form a laminatedweb via carding and cross wrapper steps. The needle punching treatmentwas performed with a number of punches of 2,500 punches/cm² to obtain anonwoven fabric having a basis weight of 540 g/m² and a thickness of 2.4mm.

<Step of Generating Ultrafine Fiber>

The nonwoven fabric obtained as described above was shrunk with hotwater at 96° C. Thereafter, the nonwoven fabric shrunk with hot waterwas impregnated with a polyvinyl alcohol (hereinafter, may beabbreviated as PVA) aqueous solution having a saponification degree of88%, which was prepared so as to have a concentration of 12% by mass.Furthermore, the nonwoven fabric was squeezed with rollers and dried byhot air having a temperature of 120° C. for 10 minutes while allowingfor migration of PVA, to obtain a PVA-impregnated sheet in which themass of PVA was 25% by mass relative to the mass of a sheet base. ThePVA-impregnated sheet thus obtained was immersed in trichloroethylene,and squeezed and compressed by a mangle ten times. Thus, dissolutionremoval of the sea portion and compression treatment of thePVA-impregnated sheet were performed to obtain a PVA-impregnated sheetin which the ultrafine fiber bundles to which PVA was applied wereentangled. The average single fiber diameter of the ultrafine fiber was4.4 μm.

<Step of Adding Elastomer>

A dimethylformamide (hereinafter, may be abbreviated as DMF) solution ofpolyurethane prepared so that the concentration of a solid contentmainly composed of polyurethane was 13% was immersed in thePVA-impregnated sheet obtained as described above. Thereafter, thesea-removing PVA-impregnated sheet immersed in DMF solution ofpolyurethane was squeezed with rollers. Then, the sheet was immersed ina DMF aqueous solution having a concentration of 30% by mass to solidifythe polyurethane. After that, PVA and DMF were removed by hot water, anda silicone oil emulsion solution adjusted to a concentration of 1% bymass was impregnated, thereby applying a silicone-based lubricant suchthat the applied amount thereof was 0.5% by mass relative to the totalmass of the mass of the fiber entanglement and the mass of thepolyurethane, and drying was performed with hot air having a temperatureof 110° C. for ten minutes. As a result, a polyurethane-impregnatedsheet having a thickness of 1.8 mm and a polyurethane mass of 33% bymass relative to the mass of the fiber entanglement was obtained. Thedensity of the polyurethane-impregnated sheet which was the fiberentanglement including the elastomer was 0.35 g/cm³.

<Step of Half-Cutting and Napping>

The polyurethane-impregnated sheet obtained as described above was cutin half such that the thickness of each part was ½. Subsequently, anapping treatment was performed by grinding the surface layer portion ofthe half-cut surface by 0.3 mm with an endless sandpaper having asandpaper grit size of 180 to obtain a napped sheet having a thicknessof 0.6 mm.

<Step of Dyeing and Finishing>

The napped sheet obtained as described above was dyed with a blackdisperse dye at 120° C. using a jet dyeing machine, andreduction-cleaned. Thereafter, a drying treatment was performed at 100°C. for 7 minutes to obtain a dyed sheet having an average single fiberdiameter of the ultrafine fiber of 4.4 μm, a basis weight of 220 g/m²,and a thickness of 0.70 mm.

<Flame Retardant Processing>

A flame retardant A was obtained by mixing 20 parts by mass of ammoniumpolyphosphate treated with a silicon oxide resin (manufactured byWellchem.com, phosphorus content: 28%, nitrogen content: 14%) as a flameretardant main component of the flame retardant, 0.2 parts by mass ofpolyoxyethylene sorbitan monostearate (nonionic surfactant) as asurfactant, 11 parts of methyl acrylate resin having a nonvolatilecontent of 50% as a binder resin, and 4 parts by mass of melaminecyanurate (nitrogen content: 49.4%), and using hydroxyethyl cellulose asa thickener. Coating processing of applying a flame retardant processingagent solution (the viscosity was adjusted to 3000 mPa·s by thethickener) containing 70% by mass of the flame retardant A to onesurface opposite to the product surface of the dyed sheet using a screencoater was performed, and then drying treatment was performed at atemperature of 100° C. for 7 minutes to obtain a sheet with a flameretardant in which the adhesion amount of the flame retardant withrespect to the mass of the artificial leather after drying was 20% bymass.

<Punching>

In the sheet with a flame retardant, a through opening portion wasformed with a punching board in which needles were planted, therebyobtaining an artificial leather (needle diameter: 1.2 mm, longitudinalpitch: 5 mm, transverse pitch: 5 mm, opening ratio: 6%). The throughopening portion after the punching was not clogged with fiber waste, theflame retardant did not stick to an edge of the opening portion, a cleanopening portion was formed, and the fiber waste and the flame retardantdid not adhere to the punching board after the punching in which dustwas blown off by air. The obtained artificial leather had excellentflame retardancy while having moderate air permeability and a flexibletexture, and had dense feels like natural suede and an elegantappearance. The tackiness of the flame retardant was 0.45 N/cm² at 60°C., 0.20 N/cm² at 40° C., and 0.14 N/cm² at 20° C. The basis weight ofthe artificial leather was 240 g/m², and the thickness was 0.72 mm. Theresults are shown in Table 1.

Example 2

An artificial leather was obtained in the same manner as in Example 1except that an ultrafine fiber-generating fiber having a sea-islandcomposite structure including an island component and a sea componentwas subjected to melt spinning using a sea-island composite spinnerethaving 16 islands under the conditions of an island/sea mass ratio of55/45, a discharge amount of 1.0 g/(min·hole), and a spinning speed of1100 m/min, and then the ratio of stretching in a spinning oil solutionbath set at 90° C. was 3.4 times. The density of thepolyurethane-impregnated sheet was 0.360 g/cm³, which was higher thanthat in Example 1, and the immersion amount of the flame retardant wassmall, so that W/W₀=0.07. The average single fiber diameter of theultrafine fiber was 2.9 μm. The results are shown in Table 1.

Example 3

A laminated web was formed using the raw stock described in Example 1via the carding and cross wrapper steps, and then a plain woven fabric(basis weight: 75 g/m²) having a warp density of 95 yarns/2.54 cm and aweft density of 76 yarns/2.54 cm, in which a twisted yarn obtained bytwisting a multifilament (average single fiber diameter: 11 μm, totalfineness: 84 dtex, 72 filaments) containing polyethylene terephthalatehaving an intrinsic viscosity (IV value) of 0.65 at 2500 T/m was usedfor both wefts and warps, was stacked on and under the laminated web.Thereafter, an artificial leather in which the average single fiberdiameter of the ultrafine fiber was 4.4 μm, the basis weight was 360g/m², and the thickness was 1.0 mm was obtained in the same manner as inExample 1 except that the needle punching treatment was performed with anumber of punches of 2,500 punches/cm² to obtain a nonwoven fabric of afiber entanglement having a basis weight of 700 g/m² and a thickness of3.0 mm. A tough artificial leather having higher strength than that ofExample 1 was obtained. The results are shown in Table 1.

Example 4

A tricot fabric was prepared with a multifilament (total fineness: 48dtex, 18 filaments) containing polyethylene terephthalate by using asingle tricot machine, and dyed with a black disperse dye to prepare adyed tricot fabric having a warp density of 32 yarns/2.54 cm and a weftdensity of 48 yarns/2.54 cm, and a low-melting-point nylon resin(softening temperature: 90° C.) as an adhesive was applied in an amountof 20 g/m² in the form of dots using a gravure roll coater, and thendried with hot air at a temperature of 100° C. to obtain a tricot withan adhesive. The tricot side was thermocompression-bonded to the dyedsheet of Example 3 with a heat roll heated to a temperature of 150° C.to obtain a composite sheet having a basis weight of 440 g/m² and athickness of 1.1 mm. The composite sheet was subjected to flameretardant processing and punched in the same manner as in Example 3 toobtain an artificial leather having a basis weight of 490 g/m² and athickness of 1.2 mm. An artificial leather having higher strength thanthat of Example 3 was obtained. The flame retardant adhered to theentire tricot, and the tricot as a single component had high flameretardancy, so that the artificial leather had high flame retardancy.The results are shown in Table 1.

Example 5

A circular knitted base fabric was knitted with a blister structureusing an interlaced yarn containing a multifilament (84 dtex/25 f,average single fiber diameter of ultrafine fibers after sea removal: 9μm) using a sea-island composite yarn using polyethylene terephthalateas the island component and polystyrene as the sea component and amultifilament (33 dtex/12 f) of polyethylene terephthalate. Anartificial leather including the fiber entanglement including theelastomer was obtained in the same manner as in Example 1 except thatthe fiber entanglement was a circular knitted base fabric. The basisweight of the artificial leather was 240 g/m², and the thickness was0.72 mm. The artificial leather which had a luxurious feeling in a lowerzone as compared with Example 1 and a relatively hard texture, and wasexcellent in water spot and punching processability was obtained. Theresults are shown in Table 1.

Example 6

An artificial leather having a basis weight of 490 g/m² and a thicknessof 1.2 mm was obtained in the same manner as in Example 4 except thatwith respect to the flame retardant, 30 parts by mass of adialkylphosphinic acid metal salt as a main component of the flameretardant and 15 parts by mass of an acrylic acid ester copolymer as abinder resin were used to obtain a flame retardant B, and a flameretardant processing agent solution containing 50% by mass of the flameretardant B was obtained. The tackiness of the flame retardant was 1.50N/cm² at 60° C., 0.50 N/cm² at 40° C., and 0.30 N/cm² at 20° C. Sincethe flame retardant had high tackiness at room temperature, theimmersion amount was smaller than that in Example 4, and the tackinessat 60° C. was high, an artificial leather having excellent flameretardancy and appearance quality was obtained although holes andpunching board needles were slightly clogged after punching. The resultsare shown in Table 1.

Example 7

An artificial leather was obtained in the same manner as in Example 4except that the opening ratio was 14%. Since the number of openingportions was larger than that in Example 4, the flame retardancy wasslightly inferior; however, an artificial leather excellent inflexibility and the like was obtained. The results are shown in Table 1.

Comparative Example 1

An artificial leather was obtained in the same manner as in Example 4except that 5 parts by mass of a methyl acrylate resin and 10 parts bymass of an acrylonitrile resin were used as binder components for theflame retardant. The tackiness was high, the opening portion was cloggedduring punching, and the air permeability was poor. The results areshown in Table 1.

Comparative Example 2

An artificial leather was obtained in the same manner as in Example 4except that the average single fiber diameter of the ultrafine fiberswas 11 μm. A rough surface touch quality with no elegance was obtained.The results are shown in Table 1.

TABLE 1 Comparative Comparative Example 1 Example 2 Example 3 Example 4Example 5 Example 6 Example 7 Example 1 Example 2 Fiber Average singlefiber 4.4 2.9 4.4 4.4 9.0 4.4 4.4 4.4 11.0 entangle- diameter ofultrafine ment fiber (μm) Fiber Nonwoven Nonwoven Nonwoven NonwovenKnitted Nonwoven Nonwoven Nonwoven Nonwoven entanglement fabric fabricfabric fabric fabric fabric fabric fabric fabric Woven/ — — Woven Woven— Woven Woven Woven Woven knitted fabric (a) fabric fabric fabric fabricfabric fabric Woven/ — — — Tricot — Tricot Tricot Tricot Tricot knittedfabric (b) Elastomer Polyurethane Density of fiber 0.35 0.36 0.40 0.400.30 0.40 0.40 0.40 0.42 entanglement including elastomer (g/cm³) FlameFlame retardant Ammonium polyphosphate Dialkylphos- Ammoniumpolyphosphate retardant main component phinic acid metal salt Main resinMethyl acrylate Acrylic acid Methyl Acrylonitrile Methyl ester acrylateacrylate Tackiness at 0.45 0.45 0.45 0.45 0.45 1.5 0.45 2.1 0.45 60° C.(N/cm²) Artificial Kinetic 0.29 0.28 0.31 0.27 0.29 0.41 0.25 0.61 0.31leather friction coefficient backing Stiffness (mm) 70 75 80 95 90 90 90105 125 material (before opening) Artificial Thickness (mm) 0.72 0.721.0 1.2 0.72 1.2 1.2 1.2 0.72 leather Basis weight (g/m²) 240 240 360360 240 360 330 360 362 W/W₀ 0.10 0.07 0.15 0.21 0.31 0.17 0.21 0.250.28 Opening ratio (%) 6 6 6 6 6 6 14 6 6 Air permeability 110 105 10090 110 95 140 65 95 (cm³/cm²/sec) Flame retardancy 25 30 20 10 40 Self-60 30 7 (mm/min) extinguished Tensile strength 50 55 70 80 40 78 70 7582 (N/cm) Appearance A A A A C A A A D quality and feel Abrasionresistance 5 4 5 5 3 5 4 5 5 Stiffness (mm) 65 70 75 90 85 85 85 100 120Water spot Acceptable Acceptable Acceptable Acceptable AcceptableAcceptable Acceptable Acceptable Acceptable Punching Good Good Good GoodGood Slightly Good Poor Good processability good

Particular embodiments have been used to detail the invention. However,it is evident to those skilled in the art that various alternations andmodifications are allowed without departing from the spirit and scope ofthe invention.

1. An artificial leather comprising: a fiber entanglement including anultrafine fiber having an average single fiber diameter of 0.1 μm ormore and 10 μm or less; and an elastomer, wherein one surface is anapped surface having a raised nap, the other surface is a flameretardant surface having a flame retardant, and the followingrequirements 1 and 2 are satisfied: requirement 1: at least the flameretardant surface has a plurality of opening portions, and requirement2: the flame retardant has a tackiness of 0.1 N/cm² or more and 2.0N/cm² or less.
 2. The artificial leather according to claim 1, whereinan opening ratio of the flame retardant surface is 1% or more and 40% orless.
 3. The artificial leather according to claim 1, wherein theartificial leather has a plurality of opening portions in each of thenapped surface and the flame retardant surface, and at least some of theopening portions are through opening portions formed to penetrate fromthe napped surface to the flame retardant surface.
 4. The artificialleather according to claim 1, wherein the fiber entanglement is formedby integrating a fiber entanglement including the ultrafine fiber and awoven/knitted fabric (a).
 5. The artificial leather according to claim1, wherein the flame retardant surface is a surface formed by stacking awoven/knitted fabric (b).
 6. The artificial leather according to claim1, wherein a presence ratio of the flame retardant in a thicknessdirection satisfies the following formula:0.001≤W/W ₀≤0.7 wherein W is a thickness (mm) from the flame retardantsurface where the flame retardant is present, and W₀ is a thickness (mm)of the entire artificial leather.
 7. The artificial leather according toclaim 1, wherein the flame retardant contains a phosphorus-basedcompound.
 8. The artificial leather according to claim 1, wherein thefiber entanglement including the elastomer has a density of 0.20 g/cm³or more and 0.50 g/cm³ or less.
 9. A production method for theartificial leather according to claim 1, comprising: applying a flameretardant having a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or lessto one surface of a napped sheet-shaped article including a fiberentanglement including ultrafine fibers having an average single fiberdiameter of 0.1 μm or more and 10 μm or less and an elastomer to form aflame retardant surface; and providing a plurality of opening portionson at least the flame retardant surface.
 10. An artificial leather or abacking material of the artificial leather comprising: a fiberentanglement including an ultrafine fiber having an average single fiberdiameter of 0.1 μm or more and 10 μm or less; and an elastomer, whereinone surface is a napped surface having a raised nap, the other surfaceis a functional surface having a functional agent, and the functionalagent has a tackiness of 0.1 N/cm² or more and 2.0 N/cm² or less.
 11. Anartificial leather or a backing material of the artificial leathercomprising: a fiber entanglement including an ultrafine fiber having anaverage single fiber diameter of 0.1 μm or more and 10 μm or less; andan elastomer, wherein one surface is a napped surface having a raisednap, the other surface is a functional surface having a functionalagent, the functional surface has a Kinetic friction coefficient of 0.15or more and 0.60 or less, and the artificial leather or the backingmaterial of the artificial leather has a stiffness of 30 mm or more and150 mm or less.
 12. An artificial leather or a backing material of theartificial leather comprising: a fiber entanglement including anultrafine fiber having an average single fiber diameter of 0.1 μm ormore and 10 μm or less; and an elastomer, wherein one surface is anapped surface having a raised nap, the other surface is a functionalsurface having a functional agent, and an adhesion amount of thefunctional agent is 2 to 30% by mass with respect to the artificialleather or the backing material of the artificial leather.